Update macos versions

Author: mborland

.github/workflows/ci.yml

@@ -253,10 +253,13 @@ jobs:
 
           - toolset: clang
             cxxstd: "11,14"
-            os: macos-11
+            os: macos-12
           - toolset: clang
             cxxstd: "20"
-            os: macos-12
+            os: macos-13
+          - toolset: clang
+            cxxstd: "20"
+            os: macos-14
 
     runs-on: ${{matrix.os}}
     container: ${{matrix.container}}