Revert dependency upgrade to see if it helps with build times and APK size (#25642)

examples/flutter_gallery/android/app/build.gradle

diff --git a/examples/flutter_gallery/android/app/build.gradle b/examples/flutter_gallery/android/app/build.gradle
index b416cee..103c0ec 100644
--- a/examples/flutter_gallery/android/app/build.gradle
+++ b/examples/flutter_gallery/android/app/build.gradle
@@ -75,7 +75,6 @@
 dependencies {
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'com.android.support.test:rules:1.0.1'
-    androidTestImplementation 'com.android.support.test:runner:1.0.2'
-    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
-    implementation 'com.android.support:appcompat-v7:27.1.1'
+    androidTestImplementation 'com.android.support.test:runner:1.0.1'
+    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
 }