[Infra] Add warning around updating/changing robolectric (#7131)

Due to issues in higher version, robolectric should remain in 4.12 for
now.

Author: rlazo

gradle/libs.versions.toml

@@ -64,7 +64,7 @@ protobufjavautil = "3.25.5"
 protoc = "3.25.5"
 quickcheck = "0.6"
 reactiveStreams = "1.0.4"
-robolectric = "4.12"
+robolectric = "4.12"            # Do not use >4.12 as it breaks the build
 runner = "1.0.2"
 rxandroid = "2.0.2"
 rxjava = "2.1.14"