Bump org.antlr:antlr4-runtime in /modules/lang-painless

Bumps [org.antlr:antlr4-runtime](https://github.com/antlr/antlr4) from 4.9.3 to 4.12.0.
- [Release notes](https://github.com/antlr/antlr4/releases)
- [Changelog](https://github.com/antlr/antlr4/blob/master/CHANGES.txt)
- [Commits](antlr/antlr4@4.9.3...4.12.0)

---
updated-dependencies:
- dependency-name: org.antlr:antlr4-runtime
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

modules/lang-painless/build.gradle

@@ -48,7 +48,7 @@ testClusters.all {
 }
 
 dependencies {
-  api 'org.antlr:antlr4-runtime:4.9.3'
+  api 'org.antlr:antlr4-runtime:4.12.0'
   api "org.ow2.asm:asm-util:${versions.asm}"
   api "org.ow2.asm:asm-tree:${versions.asm}"
   api "org.ow2.asm:asm-commons:${versions.asm}"