ci(build_base_venvs): shorten 3.15 pip-ignore comment

Author: vlad-scherbich

.gitlab/templates/build-base-venvs.yml

@@ -37,12 +37,10 @@ build_base_venvs:
       python scripts/allow_prerelease_dependencies.py
       export PIP_PRE=true
     fi
-    # requires-python in pyproject.toml stops at the versions we actually
-    # support, so pip refuses riot's `pip install -e .` of the dev package on a
-    # newer interpreter we are only trialling here. Relax that check for the
-    # trial versions so their base venv can be built without advertising
-    # support we do not have. Drop a version from this list once requires-python
-    # covers it; supported versions must never appear here.
+    # PIP_IGNORE_REQUIRES_PYTHON lets riot's `pip install -e .` install the
+    # dev package despite requires-python = ">=3.9,<3.15". 3.15 only: other
+    # matrix versions already satisfy the bound.
+    # TODO(py-315): drop this once requires-python includes 3.15
     case "$PYTHON_VERSION" in
       3.15) export PIP_IGNORE_REQUIRES_PYTHON=1 ;;
     esac