CI-unixish.yml: removed macos-13 / added macos-15-intel and macos-26 (#602)

Author: firewave

.github/workflows/CI-unixish.yml

@@ -10,7 +10,7 @@ jobs:
 
     strategy:
       matrix:
-        os: [ubuntu-22.04, ubuntu-24.04, macos-13, macos-14, macos-15]
+        os: [ubuntu-22.04, ubuntu-24.04, macos-14, macos-15, macos-15-intel, macos-26]
         compiler: [clang++]
         include:
           - os: ubuntu-22.04