"Close Editor" in the File menu did not get the correct translation value

[noneghost]

Bug Description:

"Close Editor" in the File menu did not get the correct translation value after use mater branch.

Steps to Reproduce:

After #13331

https://github.com/eclipse-theia/theia/blob/b15b639fa3b64a9518efdf3e82ea9098915ba145/packages/editor/src/browser/editor-menu.ts#L180-L184

1. Get "Close Editor" value when use "Close Editor" key, Get right value when use "close Editor" key.
2. It may be due to a mismatch in the DefaultKey values obtained by nls.

https://github.com/eclipse-theia/theia/blob/b15b639fa3b64a9518efdf3e82ea9098915ba145/packages/core/src/common/nls.ts#L90-L94

Additional Information

• Theia Version: master branch (commit id: b15b639)