tools: remove genv8constants.py

Unused after commit aa3a572 ("build: remove dtrace & etw support")
from last year. I had this vague notion that llnode also used it but
that is another script.

Fixes: #49991
PR-URL: #50023
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

.github/label-pr-config.yml

@@ -47,7 +47,7 @@ subSystemLabels:
   /^\w+\.md$/: doc
   # Different variants of Makefile and build files
   /^(?:tools\/)?(?:Makefile|BSDmakefile|create_android_makefiles)$/: build, needs-ci
-  /^tools\/(?:install\.py|genv8constants\.py|getnodeversion\.py|js2c\.py|utils\.py|configure\.d\/.*)$/: build, python, needs-ci
+  /^tools\/(?:install\.py|getnodeversion\.py|js2c\.py|utils\.py|configure\.d\/.*)$/: build, python, needs-ci
   /^vcbuild\.bat$/: build, windows, needs-ci
   /^(?:android-)?configure|node\.gyp|common\.gypi$/: build, needs-ci
   # More specific tools