Change deprecated `except!` usages

These can just be `delete` calls, with the caveat that it only takes one
argument.

app/services/groups/update_service.rb

@@ -36,7 +36,7 @@ module Groups
     end
 
     def reject_parent_id!
-      params.except!(:parent_id)
+      params.delete(:parent_id)
     end
 
     def valid_share_with_group_lock_change?

app/services/merge_requests/update_service.rb

@@ -5,14 +5,15 @@ module MergeRequests
     def execute(merge_request)
       # We don't allow change of source/target projects and source branch
       # after merge request was created
-      params.except!(:source_project_id)
-      params.except!(:target_project_id)
-      params.except!(:source_branch)
+      params.delete(:source_project_id)
+      params.delete(:target_project_id)
+      params.delete(:source_branch)
 
       merge_from_quick_action(merge_request) if params[:merge]
 
       if merge_request.closed_without_fork?
-        params.except!(:target_branch, :force_remove_source_branch)
+        params.delete(:target_branch)
+        params.delete(:force_remove_source_branch)
       end
 
       if params[:force_remove_source_branch].present?

app/services/users/update_service.rb

@@ -16,7 +16,7 @@ module Users
 
       user_exists = @user.persisted?
 
-      assign_attributes(&block)
+      assign_attributes
 
       if @user.save(validate: validate) && update_status
         notify_success(user_exists)
@@ -48,9 +48,11 @@ module Users
       success
     end
 
-    def assign_attributes(&block)
-      if @user.user_synced_attributes_metadata
-        params.except!(*@user.user_synced_attributes_metadata.read_only_attributes)
+    def assign_attributes
+      if (metadata = @user.user_synced_attributes_metadata)
+        read_only = metadata.read_only_attributes
+
+        params.reject! { |key, _| read_only.include?(key.to_sym) }
       end
 
       @user.assign_attributes(params) if params.any?