Bump errorproneCoreVersion from 2.18.0 to 2.20.0

Bumps `errorproneCoreVersion` from 2.18.0 to 2.20.0.

Updates `com.google.errorprone:error_prone_core` from 2.18.0 to 2.20.0
- [Release notes](https://github.com/google/error-prone/releases)
- [Commits](google/error-prone@v2.18.0...v2.20.0)

Updates `com.google.errorprone:error_prone_annotations` from 2.18.0 to 2.20.0
- [Release notes](https://github.com/google/error-prone/releases)
- [Commits](google/error-prone@v2.18.0...v2.20.0)

---
updated-dependencies:
- dependency-name: com.google.errorprone:error_prone_core
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: com.google.errorprone:error_prone_annotations
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

build.gradle

@@ -18,7 +18,7 @@ buildscript {
         couchdbJavaVersion = "cf377882a0a85ce1ff37b5bcc23a5389d900d66f".substring(0, 10)
         dockerComposePluginVersion = "0.16.12" // https://github.com/avast/gradle-docker-compose-plugin/releases
         errorpronePluginVersion = '3.0.1' // https://github.com/tbroyer/gradle-errorprone-plugin/releases
-        errorproneCoreVersion = '2.18.0' // https://mvnrepository.com/artifact/com.google.errorprone/error_prone_core
+        errorproneCoreVersion = '2.20.0' // https://mvnrepository.com/artifact/com.google.errorprone/error_prone_core
         antlrVersion = "4.12.0" // https://github.com/antlr/antlr4/releases
     }
     dependencies {