Remove deprecation annotation for KMS client registration.

There are some valid use-cases for which we currently don't have a replacement. So it is better to wait with deprecation until we have a replacement.

Also, update the documentation for these functions.

PiperOrigin-RevId: 616759308
Change-Id: I1802a0d0e9c8f17f2fdd7fbdc843f30135701e9c

src/main/java/com/google/crypto/tink/integration/gcpkms/GcpKmsClient.java

@@ -187,12 +187,12 @@ public Aead getAead(String uri) throws GeneralSecurityException {
    * <p>If {@code credentialPath} is present, load the credentials from that. Otherwise use the
    * default credentials.
    *
-   * @deprecated It is preferable to not register KMS clients. Instead, create the GcpKmsClient
-   *     yourself and call {@link getAead} to get a remote {@code Aead}. Use this {@code Aead} to
-   *     encrypt a keyset with {@code TinkProtoKeysetFormat.serializeEncryptedKeyset}, or to create
-   *     an envelope {@code Aead} using {@code KmsEnvelopeAead.create}.
+   * <p>In many cases, it is not necessary to register the client. For example, you can create the
+   * GcpKmsClient yourself and call {@link GcpKmsClient#getAead} to get a remote {@code Aead}. Use
+   * this {@code Aead} to encrypt a keyset for with {@code
+   * TinkProtoKeysetFormat.serializeEncryptedKeyset}, or to create an envelope {@code Aead} using
+   * {@code KmsEnvelopeAead.create}.
    */
-  @Deprecated
   public static void register(Optional<String> keyUri, Optional<String> credentialPath)
       throws GeneralSecurityException {
     GcpKmsClient client;