ci: drop Python 3.9 from CI matrices to match the ^3.10 floor

The pyproject floor is now ^3.10, so 3.9 legs can no longer `poetry
install` (^3.10 is unsatisfiable on a 3.9 interpreter) and would fail.
Remove "3.9" from every unit-test / lint / type-check / pyarrow / kernel
matrix in code-quality-checks.yml and warm-deps-cache.yml, and drop the
now-moot 3.9-kernel exclude in the warm-deps cache.

Co-authored-by: Isaac
Signed-off-by: Vikrant Puppala <vikrant.puppala@databricks.com>

Author: vikrantpuppala

.github/workflows/code-quality-checks.yml

@@ -34,7 +34,7 @@ jobs:
       labels: linux-ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
         dependency-version: ["default", "min"]
         exclude:
           - python-version: "3.12"
@@ -96,7 +96,7 @@ jobs:
       labels: linux-ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
         dependency-version: ["default", "min"]
         exclude:
           - python-version: "3.12"
@@ -246,7 +246,7 @@ jobs:
       labels: linux-ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
     steps:
       - name: Check out repository
         uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
@@ -273,7 +273,7 @@ jobs:
       labels: linux-ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
     steps:
       - name: Check out repository
         uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4

.github/workflows/warm-deps-cache.yml

@@ -86,7 +86,7 @@ jobs:
         # Mirror code-quality-checks.yml exactly so every fork check has a
         # matching warmed entry. extras: "" is the base unit-test / lint / type
         # environment; pyarrow and kernel back the two extra unit-test tiers.
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
         dependency-version: ["default", "min"]
         extras: ["", "pyarrow", "kernel"]
         exclude:
@@ -98,10 +98,6 @@ jobs:
             dependency-version: "min"
           - python-version: "3.13"
             dependency-version: "min"
-          # The kernel wheel is cp310-abi3 (Requires-Python >=3.10); the
-          # [kernel] extra is a no-op on 3.9, so there's no kernel leg to warm.
-          - python-version: "3.9"
-            extras: "kernel"
 
     name: "Warm (py ${{ matrix.python-version }}, ${{ matrix.dependency-version }} deps, extras=${{ matrix.extras || 'base' }})"