Upgrade to Gradle 4.3

While this fixes a Gradle-caused failure on Java 9, it is still failing
due to Generated annotations as seen in #3633.

Fixes #3632

Author: ejona86

examples/android/helloworld/gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,5 @@
-#Tue Jul 11 13:59:44 PDT 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.3-bin.zip

examples/android/routeguide/gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,5 @@
-#Tue Jul 11 13:59:58 PDT 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.3-bin.zip

examples/gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,5 @@
-#Tue Jul 11 13:59:22 PDT 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.3-bin.zip

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,5 @@
-#Tue Jul 11 13:58:52 PDT 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.3-bin.zip