Bump json from 20200518 to 20210307 (#184)

Bumps [json](https://github.com/douglascrockford/JSON-java) from 20200518 to 20210307.
- [Release notes](https://github.com/douglascrockford/JSON-java/releases)
- [Commits](https://github.com/douglascrockford/JSON-java/commits)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

notification-hubs-sdk/build.gradle

@@ -85,7 +85,7 @@ dependencies {
     testImplementation 'androidx.test:runner:1.3.0'
     testImplementation 'androidx.test:rules:1.3.0'
     testImplementation 'androidx.test.ext:junit:1.1.2'
-    testImplementation 'org.json:json:20200518'
+    testImplementation 'org.json:json:20210307'
     testImplementation 'org.powermock:powermock-api-mockito:1.7.4'
     testImplementation 'org.powermock:powermock-module-junit4:2.0.9'
     testImplementation 'org.powermock:powermock-module-junit4-rule-agent:2.0.9'