fix 1.5 test version spec

Author: marius311

.github/workflows/runtests.yml

@@ -8,7 +8,7 @@ jobs:
     continue-on-error: ${{ matrix.experimental == 'nightly' }}
     strategy:
       matrix:
-        julia-version: ['1.3', '1.4', '1.5'] # todo: add back nightly once it stops hanging or they allow timeout failures
+        julia-version: ['1.3', '1.4', '~1.5.0-0'] # todo: add back nightly once it stops hanging or they allow timeout failures
         os: [ubuntu-latest]
         JULIA_FFTW_PROVIDER: ['MKL'] # would be nice to get FFTW working too
       fail-fast: false