ref: move mypy stubs (#49786)

a folder named `x-stubs` gets interpreted as a stubs package even if it
is not one




<!-- Describe your PR here. -->

.github/CODEOWNERS

@@ -65,7 +65,7 @@ Makefile                                                 @getsentry/owners-sentr
 .git-blame-ignore-revs                                   @getsentry/owners-sentry-dev
 
 mypy.ini                                                 @getsentry/python-typing
-/fixtures/stubs                                          @getsentry/python-typing
+/fixtures/stubs-for-mypy                                 @getsentry/python-typing
 
 # GitHub Routing Automations - notion.so/473791bae5bf43399d46093050b77bf0
 /.github/labels.yml                                      @getsentry/open-source

mypy.ini

@@ -1,7 +1,7 @@
 [mypy]
 python_version = 3.8
-mypy_path = fixtures/mypy-stubs
-files = fixtures/mypy-stubs,
+mypy_path = fixtures/stubs-for-mypy
+files = fixtures/stubs-for-mypy,
         src/sentry/analytics/,
         src/sentry/api/bases/external_actor.py,
         src/sentry/api/bases/organization.py,