Remove unnecessary flag

Author: josephnoir

.github/workflows/main.yml

@@ -34,5 +34,4 @@ jobs:
     name: Release builds
     uses: apple/swift-nio/.github/workflows/release_builds.yml@main
     with:
-      linux_5_9_enabled: false
       linux_5_10_enabled: false

.github/workflows/pull_request.yml

@@ -76,5 +76,4 @@ jobs:
     name: Release builds
     uses: apple/swift-nio/.github/workflows/release_builds.yml@main
     with:
-      linux_5_9_enabled: false
       linux_5_10_enabled: false