chore(developer): update multer dependency for server

Removes Keyman Developer Server's transitive dependency on dicer by
updating multer to `1.4.5-lts.1`, which updates its dependency on
busboy.

See
https://github.com/expressjs/multer/pull/1097#issuecomment-1141286771
for reasoning behind use of  `-lts.1` rather than a full release
version.

At some point in the future, multer will publish a full release with
this fix, at which point we can move back to a full release version.