chore(deps): upgrade gapic-generator-java to 2.8.0 and update gax-java to 2.18.1 (#182)

- [ ] Regenerate this pull request now.

PiperOrigin-RevId: 450543911

Source-Link: googleapis/googleapis@5528344

Source-Link: https://github.com/googleapis/googleapis-gen/commit/9f6775cab1958982b88967a43e5e806af0f135db
Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiOWY2Nzc1Y2FiMTk1ODk4MmI4ODk2N2E0M2U1ZTgwNmFmMGYxMzVkYiJ9

Author: gcf-owl-bot[bot]

java-private-catalog/google-cloud-private-catalog/src/main/java/com/google/cloud/privatecatalog/v1beta1/PrivateCatalogClient.java

@@ -146,7 +146,6 @@ public static final PrivateCatalogClient create(PrivateCatalogSettings settings)
    * Constructs an instance of PrivateCatalogClient, using the given stub for making calls. This is
    * for advanced usage - prefer using create(PrivateCatalogSettings).
    */
-  @BetaApi("A restructuring of stub classes is planned, so this may break in the future")
   public static final PrivateCatalogClient create(PrivateCatalogStub stub) {
     return new PrivateCatalogClient(stub);
   }
@@ -161,7 +160,6 @@ protected PrivateCatalogClient(PrivateCatalogSettings settings) throws IOExcepti
     this.stub = ((PrivateCatalogStubSettings) settings.getStubSettings()).createStub();
   }
 
-  @BetaApi("A restructuring of stub classes is planned, so this may break in the future")
   protected PrivateCatalogClient(PrivateCatalogStub stub) {
     this.settings = null;
     this.stub = stub;
@@ -171,7 +169,6 @@ public final PrivateCatalogSettings getSettings() {
     return settings;
   }
 
-  @BetaApi("A restructuring of stub classes is planned, so this may break in the future")
   public PrivateCatalogStub getStub() {
     return stub;
   }

java-private-catalog/google-cloud-private-catalog/src/main/java/com/google/cloud/privatecatalog/v1beta1/stub/PrivateCatalogStubSettings.java

@@ -294,7 +294,6 @@ public ApiFuture<SearchVersionsPagedResponse> getFuturePagedResponse(
     return searchVersionsSettings;
   }
 
-  @BetaApi("A restructuring of stub classes is planned, so this may break in the future")
   public PrivateCatalogStub createStub() throws IOException {
     if (getTransportChannelProvider()
         .getTransportName()