permission: Set min_sdk_version to "30"

Just a cosmetic cleanup since "R" resolves to 30 as well.

Test: m
Bug: 171330443
Change-Id: I83dcc7be1ff18e6429955a0fee2596d8b0e19a25

apex/permission/Android.bp

@@ -21,7 +21,7 @@ apex {
 apex_defaults {
     name: "com.android.permission-defaults",
     updatable: true,
-    min_sdk_version: "R",
+    min_sdk_version: "30",
     key: "com.android.permission.key",
     certificate: ":com.android.permission.certificate",
     java_libs: [