[0/n] Only run tests on py3.9, not mypy

### Summary:
We don't need to run mypy on 3.9 anyway. Also it causes issues with the rest of this stack.

### Test plan:

run checks

Author: rm-openai

Diff for: .github/workflows/tests.yml

@@ -8,6 +8,9 @@ on:
     branches:
       - main
 
+env:
+  UV_FROZEN: "1"
+
 jobs:
   lint:
     runs-on: ubuntu-latest

Diff for: Makefile

@@ -37,7 +37,6 @@ snapshots-create:
 .PHONY: old_version_tests
 old_version_tests: 
 	UV_PROJECT_ENVIRONMENT=.venv_39 uv run --python 3.9 -m pytest
-	UV_PROJECT_ENVIRONMENT=.venv_39 uv run --python 3.9 -m mypy .
 
 .PHONY: build-docs
 build-docs: