Build(deps): Bump com.diffplug.spotless from 6.19.0 to 6.20.0

Bumps com.diffplug.spotless from 6.19.0 to 6.20.0.

---
updated-dependencies:
- dependency-name: com.diffplug.spotless
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

app/build.gradle

@@ -16,7 +16,7 @@ buildscript {
 }
 
 plugins {
-    id "com.diffplug.spotless" version "6.19.0"
+    id "com.diffplug.spotless" version "6.20.0"
 }
 
 apply plugin: 'com.android.application'