Remove support for the old name for the C/ObjC layering check.

PiperOrigin-RevId: 749787905

Author: thomasvl

swift/internal/feature_names.bzl

@@ -94,7 +94,6 @@ SWIFT_FEATURE_MODULAR_INDEXING = "swift.modular_indexing"
 # If enabled, when compiling an explicit C or Objectve-C module, every header
 # included by the module being compiled must belong to one of the modules listed
 # in its dependencies. This is ignored for system modules.
-SWIFT_FEATURE_LAYERING_CHECK = "swift.layering_check"
 SWIFT_FEATURE_LAYERING_CHECK_FOR_C_DEPS = "swift.layering_check_for_c_deps"
 
 # If enabled, an error will be emitted when compiling Swift code if it imports

swift/toolchains/config/compile_config.bzl

@@ -51,7 +51,6 @@ load(
     "SWIFT_FEATURE_INDEX_SYSTEM_MODULES",
     "SWIFT_FEATURE_INDEX_WHILE_BUILDING",
     "SWIFT_FEATURE_INTERNALIZE_AT_LINK",
-    "SWIFT_FEATURE_LAYERING_CHECK",
     "SWIFT_FEATURE_LAYERING_CHECK_FOR_C_DEPS",
     "SWIFT_FEATURE_LAYERING_CHECK_SWIFT",
     "SWIFT_FEATURE_MODULAR_INDEXING",
@@ -556,8 +555,7 @@ def compile_action_configs(
         ActionConfigInfo(
             actions = [SWIFT_ACTION_PRECOMPILE_C_MODULE],
             configurators = [_c_layering_check_configurator],
-            # We require both so turning off either during the migration will disable this.
-            features = [SWIFT_FEATURE_LAYERING_CHECK, SWIFT_FEATURE_LAYERING_CHECK_FOR_C_DEPS],
+            features = [SWIFT_FEATURE_LAYERING_CHECK_FOR_C_DEPS],
             not_features = [SWIFT_FEATURE_SYSTEM_MODULE],
         ),
         ActionConfigInfo(