CI: Remove now unused sources.list file

(cherry picked from commit 12e9b22777c5e8de47b6731e7b5367cf1276af21)

.github/workflows/linux_builds.yml

@@ -124,9 +124,9 @@ jobs:
       - name: Download test project
         if: ${{ matrix.test }}
         run: |
-          wget https://github.com/godotengine/regression-test-project/archive/3.x.zip
-          unzip 3.x.zip
-          mv "regression-test-project-3.x" "test_project"
+          wget https://github.com/godotengine/regression-test-project/archive/3.6.zip
+          unzip 3.6.zip
+          mv "regression-test-project-3.6" "test_project"
 
       # Editor is quite complicated piece of software, so it is easy to introduce bug here
       - name: Open and close editor

misc/ci/sources.list

@@ -1,4 +0,0 @@
-deb http://archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
-deb http://archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
-deb http://archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
-deb http://archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse