Bump checkstyle from 8.18 to 8.19 (#4834)

Bumps [checkstyle](https://github.com/checkstyle/checkstyle) from 8.18 to 8.19.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](checkstyle/checkstyle@checkstyle-8.18...checkstyle-8.19)

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

build.gradle

@@ -177,7 +177,7 @@ dependencies {
     testCompile "org.testfx:testfx-core:4.0.+"
     testCompile "org.testfx:testfx-junit5:4.0.+"
 
-    checkstyle 'com.puppycrawl.tools:checkstyle:8.18'
+    checkstyle 'com.puppycrawl.tools:checkstyle:8.19'
 }
 
 jacoco {