Update JuliaFormatter version in format check workflow

Author: odow

.github/workflows/format_check.yml

@@ -18,7 +18,7 @@ jobs:
         shell: julia --color=yes {0}
         run: |
           using Pkg
-          Pkg.add(PackageSpec(name="JuliaFormatter", version="2"))
+          Pkg.add(PackageSpec(name="JuliaFormatter", version="2.4.0"))
           using JuliaFormatter
           format(".", verbose=true)
           out = String(read(Cmd(`git diff`)))