build: cleanup in .gitignore

* explicitly unignore files that we track.

The following are not created anymore (only as subdirs of v8/gypfiles)
/deps/v8/src/debug/obj
deps/v8/src/Debug/
deps/v8/src/Release/
deps/v8/src/inspector/Debug/
deps/v8/src/inspector/Release/

PR-URL: https://github.com/nodejs/node/pull/23180
Refs: https://github.com/nodejs/node/pull/23156


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>