Mute test151MachineDependentHeapWithSizeOverride (elastic#131840)

Related to issue elastic#123437.

Author: jozala

muted-tests.yml

@@ -501,3 +501,6 @@ tests:
 - class: org.elasticsearch.packaging.test.PackageUpgradeTests
   method: test12SetupBwcVersion
   issue: https://github.com/elastic/elasticsearch/issues/131791
+- class: org.elasticsearch.packaging.test.DockerTests
+  method: test151MachineDependentHeapWithSizeOverride
+  issue: https://github.com/elastic/elasticsearch/issues/120978