GHA: quote OCaml version numbers

MisterDA · MisterDA · commit 2c3c97fd876c · 2025-03-19T18:08:07.000-03:00
Otherwise they're wrongly interpreted as integers or floating-point
numbers.
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
@@ -16,10 +16,10 @@ jobs:
           - macos-latest
           - windows-latest
         ocaml-compiler:
-          - 5
+          - '5'
         include:
           - os: ubuntu-latest
-            ocaml-compiler: 4.11
+            ocaml-compiler: '4.11'
 
     runs-on: ${{ matrix.os }}
 
