feat!: remove methods with Optional params from VertexCredential.Builder

PiperOrigin-RevId: 879065249

Author: tilgalas

core/src/main/java/com/google/adk/models/VertexCredentials.java

@@ -38,16 +38,11 @@ public static Builder builder() {
   /** Builder for {@link VertexCredentials}. */
   @AutoValue.Builder
   public abstract static class Builder {
-    public abstract Builder setProject(Optional<String> value);
 
     public abstract Builder setProject(@Nullable String value);
 
-    public abstract Builder setLocation(Optional<String> value);
-
     public abstract Builder setLocation(@Nullable String value);
 
-    public abstract Builder setCredentials(Optional<GoogleCredentials> value);
-
     public abstract Builder setCredentials(@Nullable GoogleCredentials value);
 
     public abstract VertexCredentials build();