Change Actions minimum nightly

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
       matrix:
         toolchain:
           # Run against a "known good" nightly
-          - nightly-2023-01-13
+          - nightly-2023-05-31
           # Check for breakage on latest nightly
           - nightly
 
@@ -57,7 +57,7 @@ jobs:
     strategy:
       matrix:
         toolchain:
-          - nightly-2023-01-13
+          - nightly-2023-05-31
           - nightly
     continue-on-error: ${{ matrix.toolchain == 'nightly' }}
     runs-on: ubuntu-latest