Update crate_universe to allow re-pinning precise packages with pins

[UebelAndre]

This change corrects the parsing logic of CARGO_BAZEL_REPIN to solve for the following issue

CARGO_BAZEL_REPIN=ahash@0.7.7 bazel build //...

ERROR: /home/user/Code/factory/WORKSPACE.bazel:162:12: fetching crates_repository rule //external:crates_io: Traceback (most recent call last):
	File "/home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/rules_rust/crate_universe/private/crates_repository.bzl", line 59, column 50, in _crates_repository_impl
		metadata_path = splice_workspace_manifest(
	File "/home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/rules_rust/crate_universe/private/splicing_utils.bzl", line 178, column 12, in splice_workspace_manifest
		execute(
	File "/home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/rules_rust/crate_universe/private/common_utils.bzl", line 54, column 13, in execute
		fail(_EXECUTE_ERROR_MESSAGE.format(
Error in fail: Command [/home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/crates_io/cargo-bazel, "splice", "--output-dir", /home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/crates_io/splicing-output, "--splicing-manifest", /home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/crates_io/splicing_manifest.json, "--config", /home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/crates_io/cargo-bazel.json, "--cargo", /home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/rust_linux_x86_64__x86_64-unknown-linux-gnu__stable_tools/bin/cargo, "--rustc", /home/user/.cache/bazel/_bazel_user/2a4a06230c9b85a2073801b413943939/external/rust_linux_x86_64__x86_64-unknown-linux-gnu__stable_tools/bin/rustc, "--cargo-lockfile", /home/user/Code/factory/Cargo.lock] failed with exit code 1.
STDOUT ------------------------------------------------------------------------

STDERR ------------------------------------------------------------------------

warning: unused config key `source.crates-io.index` in `/tmp/.tmpAWm8NK/.cargo/config.toml`
error: There are multiple `ahash` packages in your project, and the specification `ahash` is ambiguous.
Please re-run this command with one of the following specifications:
  ahash@0.7.7
  ahash@0.8.7

Error: Failed to update lockfile: exit status: 101

After this <package_name>=<pin> can be used to distinguish which of the multiple versions of crates available in the lockfile should be updated to the assigned pin.

[scentini]

Thanks!