chore(.github): use ubuntu-22.04

Some issues arose since ubuntu 24:
- SBOM directory: mkdir /tmp/melange-workspace-2571162140/melange-out: permission denied
- Command failed with: bwrap: setting up uid map: Permission denied

Signed-off-by: Massimiliano Giovagnoli <massimiliano.giovagnoli@chainguard.dev>

Author: maxgio92

.github/workflows/e2e.yaml

@@ -12,7 +12,7 @@ env:
 jobs:
   examples:
     name: build examples
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
 
     permissions:
       contents: read

.github/workflows/go-tests.yaml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
 
     permissions:
       contents: read

.github/workflows/melange-test-pipelines.yaml

@@ -41,7 +41,7 @@ jobs:
     needs:
       - build-melange
     # TODO: Set up a larger runner for this.
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
 
     permissions:
       contents: read