Bump the min sdk of Tethering

This is required because we are bumping the min sdk of NetworkStack
which this depends on.

Test: build locally + aapt2 dump badging

Bug: 444168252

Flag: build.RELEASE_DEPRECATE_MAINLINE_R_SUPPORT
Change-Id: Idbff03cdcca9955a4759c19866895f755abedaaf

Tethering/tests/privileged/Android.bp

@@ -53,5 +53,8 @@ android_test {
         "TetheringApiCurrentLib",
     ],
     compile_multilib: "both",
-    min_sdk_version: "30",
+    min_sdk_version: select(release_flag("RELEASE_DEPRECATE_MAINLINE_R_SUPPORT"), {
+        true: "31",
+        default: "30",
+    }),
 }

Tethering/tests/unit/Android.bp

@@ -45,7 +45,10 @@ java_library {
 
 java_defaults {
     name: "TetheringTestsDefaults",
-    min_sdk_version: "30",
+    min_sdk_version: select(release_flag("RELEASE_DEPRECATE_MAINLINE_R_SUPPORT"), {
+        true: "31",
+        default: "30",
+    }),
     srcs: [
         "src/**/*.java",
         "src/**/*.kt",