`uglify:moment` task fails due to missing source file

[desrosj]

Follow up to #64393.

When running the build script, the following notice is output:

Running "uglify:moment" (uglify) task
>> Destination src/wp-includes/js/dist/vendor/moment.min.js not written because src files were empty.
>> No files created.

This fixes a bug where the moment.js file is not present before the uglify:all Grunt task runs by moving the copy-vendor-scripts into the build:js task _before uglify:all`.

Trac ticket: Core-65006.

## Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Sonnet 4.6
Used for: Comparing the current behavior to before the recent build script changes to determine what was different.

[peterwilsoncc]

In 62189:

Build/Test Tools: Copy vendor scripts earlier in the build.

Relocates the copy-vendor-scripts to run during the the build:js portion of the build script. This ensures the JavaScript files are in place before the uglify:all task is run.

Follow up to r61438

Props desrosj.
Fixes #65006. See #64393.

[peterwilsoncc]

Reopening for merge to the 7.0 branch following clarification of process in ​the #core-committers slack channel.

[desrosj]

In 62275:

Build/Test Tools: Copy vendor scripts earlier in the build.

Relocates the copy-vendor-scripts to run during the the ​build:js portion of the build script. This ensures the JavaScript files are in place before the uglify:all task is run.

Follow up to r61438.

Reviewed by desrosj, peterwilsoncc.
Merges [62189] to the 7.0 branch.

Props desrosj, peterwilsoncc.
Fixes #65006. See #64393.