Adjust the platform definition for the erlang git master pipeline (#7964) (#7975)

by using the more selective constraint value

(cherry picked from commit a7365d0)

Co-authored-by: Rin Kuryloski <[email protected]>

Author: mergify[bot]

bazel/platforms/BUILD.bazel

@@ -68,7 +68,7 @@ platform(
 platform(
     name = "erlang_linux_git_master_platform",
     constraint_values = [
-        "@erlang_config//:erlang_26",
+        "@erlang_config//:erlang_26_unknown",
         "@elixir_config//:elixir_1_14",
     ],
     parents = ["@rbe//config:platform"],