Don't do JET.jl testing on pre-release (#1296)

Author: KnutAM

.github/workflows/Test.yml

@@ -34,7 +34,7 @@ jobs:
           Pkg.add("JET")
           Pkg.develop(path = pwd())
           include(joinpath(pwd(), "test/jet.jl"))
-        if: ${{ matrix.os == 'ubuntu-latest' && matrix.julia-version != 'nightly' }}
+        if: ${{ matrix.os == 'ubuntu-latest' && matrix.julia-version != 'pre' }}
       - uses: julia-actions/julia-processcoverage@v1
         with:
           directories: 'src,ext'