Fix IdentityBinaryExpression warnings in support library

Error prone found these 2 bugs in our code.

Bug: 35965190
Test: ./gradlew assembleErrorProne
Change-Id: I97fba6f70dcdc979567e94f58ee1676e3736f0b3

src/main/groovy/android/support/SupportLibraryPlugin.groovy

@@ -170,7 +170,6 @@ class SupportLibraryPlugin implements Plugin<Project> {
                             '-Xep:TypeParameterUnusedInFormals:WARN',
                             '-Xep:MissingOverride:WARN',
                             '-Xep:ArrayToString:WARN',
-                            '-Xep:IdentityBinaryExpression:WARN',
                             '-Xep:MislabeledAndroidString:WARN',
                             '-Xep:SelfEquals:WARN',
                             '-Xep:RectIntersectReturnValueIgnored:WARN',