Temporarily disable nullaway plugin

The nullaway plugin fails in errorprone build with stubs generated from
the API signature files, although the nullability information between
the from-text and from-source stubs are identical. Below is the failing
error message:
```
packages/apps/Settings/src/com/android/settings/accessibility/AccessibilitySettingsContentObserver.java:54: error: An unhandled exception was thrown by the Error Prone static analysis plugin.
            contentResolver.registerContentObserver(uri, false, this);
                           ^
     Please report this at https://github.com/google/error-prone/issues/new and include the following:

     error-prone version: 2.15.0
     BugPattern: NullAway
     Stack Trace:
     com.google.common.util.concurrent.UncheckedExecutionException: java.lang.RuntimeException: expected call to iterator(), instead saw null
```
The error message indicates that the nullaway plugin is throwing an
uncaught exception. Given that the plugin has been recently introduced
to the tree and is currently being only used by Settings, this change
proposes to temporarily disable the plugin to unblock the from-text stub
generation feature and re-enable the plugin once the issue is fixed.

Test: m Settings
Bug: 306242755
Bug: 304077181
Change-Id: I617d8f20ceeefb339b3c1f8cd03af94a8c37fd39

Android.bp

@@ -122,12 +122,13 @@ android_library {
 
     plugins: ["androidx.room_room-compiler-plugin"],
 
-    errorprone: {
-        extra_check_modules: ["//external/nullaway:nullaway_plugin"],
-        javacflags: [
-            "-XepOpt:NullAway:AnnotatedPackages=com.android.settings",
-        ],
-    },
+    // TODO: b/307330031 - Re-enable the nullaway plugin when the issue is fixed.
+    // errorprone: {
+    //     extra_check_modules: ["//external/nullaway:nullaway_plugin"],
+    //     javacflags: [
+    //         "-XepOpt:NullAway:AnnotatedPackages=com.android.settings",
+    //     ],
+    // },
 
     libs: [
         "telephony-common",