Remove retired macos image from test matrix in CI

.github/workflows/build-and-test.yml

@@ -69,12 +69,6 @@ jobs:
             sdk-preview: true
             runtime: -x64
             codecov: false
-          - os: macos-13 # macos-latest runs on arm64 runners where libgdiplus is unavailable
-            framework: net10.0
-            sdk: 10.0.x
-            sdk-preview: true
-            runtime: -x64
-            codecov: false
           - os: macos-26
             framework: net10.0
             sdk: 10.0.x
@@ -99,11 +93,6 @@ jobs:
             sdk: 8.0.x
             runtime: -x64
             codecov: false
-          - os: macos-13 # macos-latest runs on arm64 runners where libgdiplus is unavailable
-            framework: net8.0
-            sdk: 8.0.x
-            runtime: -x64
-            codecov: false
           - os: macos-26
             framework: net8.0
             sdk: 8.0.x