Deps: Replace android material with androidx appcompat in wordpress cmt

Removing the 'android.material' dependency wasn't enough by itself as
the build was then failing. Adding the transient 'androidx.appcompat'
dependency was actually required in order to make the build successful
again.

Then, and just like it was done on this
(7db2a43) change, the seemingly unused
'androidx.appcompat' dependency advise got suppressed as well.

------------------------------------------------------------------------

This replacement was suggested by the dependency analysis report,
see below:

Advice for :wordpress-comments
Unused dependencies which should be removed:
  implementation 'com.google.android.material:material:1.2.1'

Author: ParaskP7

wordpress-comments/build.gradle

@@ -38,13 +38,22 @@ android {
 dependencies {
     implementation aztecProjectDependency
 
-    implementation 'com.google.android.material:material:1.0.0'
+    implementation 'androidx.appcompat:appcompat:1.0.0'
     implementation "org.wordpress:utils:$wordpressUtilsVersion"
 
     testImplementation "junit:junit:$jUnitVersion"
     testImplementation "org.robolectric:robolectric:$robolectricVersion"
 }
 
+dependencyAnalysis {
+    issues {
+        onUnusedDependencies {
+            // This dependency is actually needed otherwise the build fails in multiple places.
+            exclude("androidx.appcompat:appcompat")
+        }
+    }
+}
+
 project.afterEvaluate {
     publishing {
         publications {