Bug 1775183 - Remove fork_interpose.py. r=firefox-build-system-review…

…ers,nalexander

Its use was removed in bug 1720591.

Differential Revision: https://phabricator.services.mozilla.com/D149840

.flake8

@@ -17,7 +17,6 @@ exclude =
     netwerk/protocol/http/make_incoming_tables.py,
     python/devtools/migrate-l10n/migrate/main.py,
     python/l10n/fluent_migrations,
-    python/mozbuild/mozbuild/fork_interpose.py,
     security/manager/ssl/tests/unit,
     servo/components/style,
     testing/condprofile/condprof/android.py,

tools/lint/black.yml

@@ -4,7 +4,6 @@ black:
     exclude:
         - gfx/harfbuzz/src/meson.build
         - layout/style/ServoCSSPropList.mako.py
-        - python/mozbuild/mozbuild/fork_interpose.py
         - python/mozbuild/mozbuild/test/frontend/data/reader-error-syntax/moz.build
         - testing/mozharness/configs/test/test_malformed.py
         - testing/web-platform/tests