chore(build): turn off extension hash cache on 3.10 (#14367)

Multiple PRs experienced `tests/smoke_test.py` failing on
build_base_venv jobs, blocking merging those PRs, examples include

- #14310
- #14353

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [ ] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Author: taegyunkim

.gitlab/templates/cached-testrunner.yml

@@ -18,15 +18,16 @@
     else
         source $EXT_CACHE_VENV/bin/activate
     fi
-    python scripts/gen_ext_cache_scripts.py
-    deactivate
-    $SHELL scripts/restore-ext-cache.sh
-  after_script: |
-    set -e -o pipefail
-    source $EXT_CACHE_VENV/bin/activate
-    python scripts/gen_ext_cache_scripts.py
-    deactivate
-    $SHELL scripts/save-ext-cache.sh
+    # Turn off ext build cache as it makes smoke_test very flaky on 3.10
+    # python scripts/gen_ext_cache_scripts.py
+    # deactivate
+    # $SHELL scripts/restore-ext-cache.sh
+  # after_script: |
+  #   set -e -o pipefail
+  #   source $EXT_CACHE_VENV/bin/activate
+  #   python scripts/gen_ext_cache_scripts.py
+  #   deactivate
+  #   $SHELL scripts/save-ext-cache.sh
   cache:
     # Share pip/sccache between jobs of the same Python version
     - key: v1-build_base_venvs-${{PYTHON_VERSION}}-cache-{current_month}