Update workflows to use ubuntu-latest (#2477)

* Update workflows to use ubuntu-latest

* Stop testing process_pr for Python 3.6

Author: iarspider

Diff for: .github/workflows/test-changes.yaml

@@ -8,7 +8,7 @@ on:
       - master
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         python-version: [ '3.x' ]

Diff for: .github/workflows/test-process-pr.yaml

@@ -8,10 +8,10 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.6", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
 
     steps:
       - uses: MathRobin/[email protected]

Diff for: tests/run_pr_tests.sh

@@ -1,7 +1,7 @@
 #!/bin/bash -xe
 INSTALL_REQS=0
 if [ ! -d venv ];  then
-  python3.6 -m venv venv
+  python3.9 -m venv venv
   INSTALL_REQS=1
 fi