Remove conditionals in skylark apple rules for presence of objc.dynamic_framework_dir

--
PiperOrigin-RevId: 143700968
MOS_MIGRATED_REVID=143700968
diff --git a/tools/build_defs/apple/swift.bzl b/tools/build_defs/apple/swift.bzl
index d4c3e8b..d8032ae 100644
--- a/tools/build_defs/apple/swift.bzl
+++ b/tools/build_defs/apple/swift.bzl
@@ -249,8 +249,7 @@
     objc_module_maps += objc.module_map
 
     framework_dirs += _parent_dirs(objc.framework_dir)
-    # TODO(cparsons): Remove getattr call once dynamic_framework_dir is stable.
-    framework_dirs += _parent_dirs(getattr(objc, "dynamic_framework_dir", []))
+    framework_dirs += _parent_dirs(objc.dynamic_framework_dir)
 
     # objc_library#copts is not propagated to its dependencies and so it is not
     # collected here. In theory this may lead to un-importable targets (since