revert(ci): restore GitHub-hosted runners (#14)

## Summary
- revert the self-hosted runner migration
- restore GitHub-hosted workflow execution for this repo
- remove the netcup runner dependency from CI

#### Test plan
- [x] Confirmed the revert removes `self-hosted` from the workflow files

Author: barrettruth

.github/workflows/ci.yaml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   changes:
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     outputs:
       lua: ${{ steps.changes.outputs.lua }}
     steps:
@@ -26,7 +26,7 @@ jobs:
               - 'selene.toml'
 
   lua-format:
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     needs: changes
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:
@@ -38,7 +38,7 @@ jobs:
           args: --check .
 
   lua-lint:
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     needs: changes
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:
@@ -49,7 +49,7 @@ jobs:
           args: --display-style quiet .
 
   lua-typecheck:
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     needs: changes
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:

.github/workflows/luarocks.yaml

@@ -11,7 +11,7 @@ jobs:
 
   publish:
     needs: ci
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v4

.github/workflows/quality.yaml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   changes:
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     outputs:
       lua: ${{ steps.changes.outputs.lua }}
       markdown: ${{ steps.changes.outputs.markdown }}
@@ -30,7 +30,7 @@ jobs:
 
   lua-format:
     name: Lua Format Check
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     needs: changes
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:
@@ -43,7 +43,7 @@ jobs:
 
   lua-lint:
     name: Lua Lint Check
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     needs: changes
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:
@@ -56,7 +56,7 @@ jobs:
 
   lua-typecheck:
     name: Lua Type Check
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     needs: changes
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:
@@ -70,7 +70,7 @@ jobs:
 
   markdown-format:
     name: Markdown Format Check
-    runs-on: [self-hosted, linux, x64, netcup, general]
+    runs-on: ubuntu-latest
     needs: changes
     if: ${{ needs.changes.outputs.markdown == 'true' }}
     steps: