tools: do not override V8's gitignore

The root .gitignore contains "node", which causes all of
deps/v8/tools/node to be ignored. That is somewhat inconvenient when
updating V8.

PR-URL: #18010
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

.gitignore

@@ -115,3 +115,6 @@ icu_config.gypi
 deps/uv/.github/
 deps/uv/docs/code/
 deps/uv/docs/src/guide/
+
+# do not override V8's .gitignore
+!deps/v8/**