Update nightly.yml

Author: opensource-krzysztof

.github/workflows/nightly.yml

@@ -98,7 +98,7 @@ jobs:
         compiler: [{c: cl, cxx: cl}]
         shared_library: ['ON', 'OFF']
         static_hwloc: ['ON', 'OFF']
-        generator: ['Ninja', 'NMake Makefiles', 'Unix Makefiles']
+        generator: ['Unix Makefiles']
         umfd_lib: ['ON', 'OFF']
 
     runs-on: windows-latest