remove macos-11 runner label support which was dropped in Jun 2024

https://github.blog/changelog/2024-05-20-actions-upcoming-changes-to-github-hosted-macos-runners/#macos-11-deprecation-and-removal

README.md

@@ -60,7 +60,7 @@ test.yaml:5:11: character '\' is invalid for branch and tag names. only special
   |
 5 |       - 'v\d+'
   |           ^~~~
-test.yaml:10:28: label "linux-latest" is unknown. available labels are "windows-latest", "windows-2022", "windows-2019", "windows-2016", "ubuntu-latest", "ubuntu-22.04", "ubuntu-20.04", "ubuntu-18.04", "macos-latest", "macos-12", "macos-12.0", "macos-11", "macos-11.0", "macos-10.15", "self-hosted", "x64", "arm", "arm64", "linux", "macos", "windows". if it is a custom label for self-hosted runner, set list of labels in actionlint.yaml config file [runner-label]
+test.yaml:10:28: label "linux-latest" is unknown. available labels are "windows-latest", "windows-2022", "windows-2019", "windows-2016", "ubuntu-latest", "ubuntu-22.04", "ubuntu-20.04", "ubuntu-18.04", "macos-latest", "macos-12", "macos-12.0", "macos-11.0", "macos-10.15", "self-hosted", "x64", "arm", "arm64", "linux", "macos", "windows". if it is a custom label for self-hosted runner, set list of labels in actionlint.yaml config file [runner-label]
    |
 10 |         os: [macos-latest, linux-latest]
    |                            ^~~~~~~~~~~~~

rule_runner_label.go

@@ -58,7 +58,6 @@ var allGitHubHostedRunnerLabels = []string{
 	"macos-12-large",
 	"macos-12",
 	"macos-12.0",
-	"macos-11",
 	"macos-11.0",
 }
 
@@ -104,7 +103,6 @@ var defaultRunnerOSCompats = map[string]runnerOSCompat{
 	"macos-12-large":         compatMacOS120L,
 	"macos-12":               compatMacOS120,
 	"macos-12.0":             compatMacOS120,
-	"macos-11":               compatMacOS110,
 	"macos-11.0":             compatMacOS110,
 	"windows-latest":         compatWindows2022,
 	"windows-latest-8-cores": compatWindows2022,