fix(deps): update dependency androidx.test.ext:junit to v1.2.1 (#372)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [androidx.test.ext:junit](https://developer.android.com/testing) |
`1.1.5` -> `1.2.1` |
[![age](https://developer.mend.io/api/mc/badges/age/maven/androidx.test.ext:junit/1.2.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/maven/androidx.test.ext:junit/1.2.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/maven/androidx.test.ext:junit/1.1.5/1.2.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
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|

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example/android/app/build.gradle

@@ -56,6 +56,6 @@ flutter {
 
 dependencies {
     testImplementation 'junit:junit:4.13.2'
-    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
+    androidTestImplementation 'androidx.test.ext:junit:1.2.1'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.6.1'
 }