Update yew requirement from 0.20 to 0.21

[dependabot]

Updates the requirements on yew to permit the latest version.

Changelog

Sourced from yew's changelog.

✨ yew 0.21.0 (2023-09-23)

Changelog

🛠 Fixes

• Fix rust-analyzer non_camel_case_types warning. [[@​Sean Bruton](https://github.com/Sean Bruton), #3388]
• Fix incorrect text escaping during SSR. [[@​Tim Kurdov](https://github.com/Tim Kurdov), #3381]
• Fix top-level reconciliation in portals. [@​WorldSEnder, #3020]
• Fix clippy::let_unit_value lint in propless components. [@​WorldSEnder, #2970]

⚡️ Features

• Updated the docs of set_event_bubbling. [[@​Tim Kurdov](https://github.com/Tim Kurdov), #3391]
• feat: support arrays for Classes/classes!(). [@​Pouriya, #3393]
• Mark VNode as #[must_use]. [[@​Kaede Hoshikawa](https://github.com/Kaede Hoshikawa), #3387]
• Add IntoPropValue implementation to convert from Cows to AttrValue. [[@​Tim Kurdov](https://github.com/Tim Kurdov), #3346]
• Remove compatibility code before 1.64. [[@​Kaede Hoshikawa](https://github.com/Kaede Hoshikawa), #3379]
• Keep checked attribute for elements without special handling. [[@​Muhammad Hamza](https://github.com/Muhammad Hamza), #3373]
• feat: implement hydration for vraw. [[@​Dillen Meijboom](https://github.com/Dillen Meijboom), #3245]
• Add webkitdirectory to the boolean attributes list. [[@​Julius Lungys](https://github.com/Julius Lungys), #3214]
• Incremental performance improvements to element creation. [[@​Greg Johnston](https://github.com/Greg Johnston), #3169]
• Make VList's children Rc'ed. [[@​Kaede Hoshikawa](https://github.com/Kaede Hoshikawa), #3050]
• Update dependencies. [[@​Muhammad Hamza](https://github.com/Muhammad Hamza), #3171]
• Pass string types to Html props. [[@​Cecile Tonglet](https://github.com/Cecile Tonglet), #2872]
• Implement an internal DomSlot for positioning instead of NodeRef. [@​WorldSEnder, #3048]
• Prefer pop_first if it is available. [[@​Kaede Hoshikawa](https://github.com/Kaede Hoshikawa), #3084]
• Add method map() on Children to wrap easily. [[@​Cecile Tonglet](https://github.com/Cecile Tonglet), #3039]
• Reentrant event listeners. [@​WorldSEnder, #3037]
• Add impl IntoIterator on &Classes. [[@​Cecile Tonglet](https://github.com/Cecile Tonglet), #3038]
• Assert there are no circular references. [@​WorldSEnder, #3025]

🚨 Breaking changes

• Remove special handing of struct fields of type Option in derive(Properties). [[@​Tim Kurdov](https://github.com/Tim Kurdov), #3398]
• Agent v2. [[@​Kaede Hoshikawa](https://github.com/Kaede Hoshikawa), #2773]
• Update signature of use_prepared_state/use_transitive_state. [[@​Muhammad Hamza](https://github.com/Muhammad Hamza), #3376]
• Make signature of use_future_with consistent. [[@​Muhammad Hamza](https://github.com/Muhammad Hamza), #3372]
• Allow any type to be used as Children (take 2). [[@​Kaede Hoshikawa](https://github.com/Kaede Hoshikawa), #3289]
• Enable PartialEq for all virtual dom types. [[@​Kaede Hoshikawa](https://github.com/Kaede Hoshikawa), #3206]
• Pass hook dependencies as the first function argument. [[@​Arniu Tseng](https://github.com/Arniu Tseng), #2861]
• Make Classes cheap to clone. [[@​Cecile Tonglet](https://github.com/Cecile Tonglet), #3021]

✨ yew-router 0.18.0 (2023-09-xx)

Changelog

⚡️ Features

• Update dependencies. [[@​Muhammad Hamza](https://github.com/Muhammad Hamza), #3171]
• Only handle "normal" clicks on s. [[@​Kai Salmon](https://github.com/Kai Salmon), #3056]

... (truncated)

Commits

• 4c3bcdc (cargo-release) version {{crate_name}}-v{{version}}
• 5e823e7 Prepare for 0.21 release (#3412)
• 30e2d54 Added a note about using suspension (#3410)
• 189a729 Remove unneded package-lock.json (#3411)
• 5bab22d Add neovim configuration to docs (#3400)
• 0c802f8 Documentation changes related to context code snippets (#3396)
• 0f2fc59 Updated the docs of set_event_bubbling (#3391)
• ca2aa2a Bump the cargo dependencies with 36 updates (#3408)
• a2786b1 Improve Context API docs (#3409)
• 954b0ec Correct minor mistakes in website (#3405)
• Additional commits viewable in compare view

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[dependabot]

Looks like yew is up-to-date now, so this is no longer needed.