Update the Gradle wrapper to 5.1.1

This is required to use Kotlin plugins like the Jetifier with
Gradle's embedded Kotlin runtime.

#145
Bug: 113575309
Change-Id: I4d11d30d7944fb95a2c1c2f19f0762d55eda0024

Author: Stewart Miles

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.10-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.1.1-bin.zip