Bump annotations from 20.0.0 to 20.1.0 in /modules/mysql (#3198)

Bumps [annotations](https://github.com/JetBrains/java-annotations) from 20.0.0 to 20.1.0.
- [Release notes](https://github.com/JetBrains/java-annotations/releases)
- [Changelog](https://github.com/JetBrains/java-annotations/blob/master/CHANGELOG.md)
- [Commits](JetBrains/java-annotations@20.0.0...20.1.0)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

modules/mysql/build.gradle

@@ -15,5 +15,5 @@ dependencies {
     testCompile testFixtures(project(':r2dbc'))
     testCompile 'dev.miku:r2dbc-mysql:0.8.1.RELEASE'
 
-    compileOnly 'org.jetbrains:annotations:20.0.0'
+    compileOnly 'org.jetbrains:annotations:20.1.0'
 }