Update python Docker tag to v3.12

This MR contains the following updates:

Package	Type	Update	Change
python	image	minor	3.9 -> 3.12
python	final	minor	3.9-slim -> 3.12-slim

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.gitlab-ci.yml

@@ -22,7 +22,7 @@ stages:
       - Dockerfile
 
 run_test_cases:
-  image: python:3.9
+  image: python:3.12
   stage: test
   before_script:
     - *install_requirements
@@ -35,7 +35,7 @@ run_test_cases:
       junit: report.xml
 
 check_coverage:
-  image: python:3.9
+  image: python:3.12
   stage: test
   needs: ["run_test_cases"]
   before_script:
@@ -51,7 +51,7 @@ check_coverage:
         path: coverage.xml
 
 check_style:
-  image: python:3.9
+  image: python:3.12
   stage: test
   needs: ["run_test_cases"]
   before_script: