Update gradle wrapper to 5.6.1

This bug-fix release contains changes to Gradle 5.6:

- Unable to publish artifacts with custom classifier/extension from java project with Gradle 5.6 (gradle/gradle#10287)
- Regression in 5.6 signArchives (Duplicate key) (gradle/gradle#10302)
- Regression setting version for ArchiveTasks in 5.6 (gradle/gradle#10311)
- A failure occurred while executing org.jetbrains.kotlin.compilerRunner.GradleKotlinCompilerWork (gradle/gradle#10317)
- DirectoryFileTree breaks SourceTask since 5.6 (gradle/gradle#10322)
- Regression: Unable to pass java.util.Properties object using Worker API in Gradle 5.6 (gradle/gradle#10323)
- Unable to publish multiple publications with same coordinates (gradle/gradle#10333)
- Gradle 5.6 - RuntimeException: Unable to load FastStringService (gradle/gradle#10347)

We recommend that you use Gradle 5.6.1 over 5.6.

## Upgrade Instructions

Switch your build to use Gradle 5.6.1 by updating your wrapper properties:

`./gradlew wrapper --gradle-version=5.6.1`

Standalone downloads are available at https://gradle.org/install.

## Reporting Problems

If you find a problem with Gradle, please file a bug on [GitHub Issues](https://github.com/gradle/gradle/issues) adhering to our issue guidelines. If you're not sure you're encountering a bug, please use the [forum](https://discuss.gradle.org/c/help-discuss).

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 distributionSha256Sum=8d78b2ed63e7f07ad169c1186d119761c4773e681f332cfe1901045b1b0141bc
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.5-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.1-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists