[Fix] Downgrade ButterKnife to fix build.

Author: zhanghai

sample/build.gradle

@@ -35,7 +35,7 @@ android {
 dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
     implementation 'androidx.appcompat:appcompat:1.0.2'
-    implementation 'com.jakewharton:butterknife:9.0.0-rc3'
-    annotationProcessor 'com.jakewharton:butterknife-compiler:9.0.0-rc3'
+    implementation 'com.jakewharton:butterknife:9.0.0-rc1'
+    annotationProcessor 'com.jakewharton:butterknife-compiler:9.0.0-rc1'
     implementation project(':library')
 }