Make addUnwantedCapability method public

Allow apps to specify a list of capabilities that network must not have
in order to satisfy the request.

Bug: 72828388
Test: m -j
Change-Id: I91ee54963f7b92899c7a107b3a450b268c62fd8d

core/java/android/net/NetworkRequest.java

@@ -229,7 +229,6 @@ public class NetworkRequest implements Parcelable {
          *
          * @param capability The capability to add to unwanted capability list.
          * @return The builder to facilitate chaining.
-         * @hide
          */
         public Builder addUnwantedCapability(@NetworkCapabilities.NetCapability int capability) {
             mNetworkCapabilities.addUnwantedCapability(capability);