revert some CI changes

Author: mcabbott

.buildkite/pipeline.yml

@@ -3,10 +3,10 @@ env:
   # SECRET_CODECOV_TOKEN: "..."
 
 steps:
-  - label: "Julia 1.6"
+  - label: "Julia 1.5"
     plugins:
       - JuliaCI/julia#v0.5:
-          version: 1.6
+          version: 1.5
       - JuliaCI/julia-test#v0.3: ~
       # - JuliaCI/julia-coverage#v0.3:
       #     codecov: true

.github/workflows/ci-julia-nightly.yml

@@ -48,10 +48,6 @@ jobs:
         env:
           JULIA_NUM_THREADS: ${{ matrix.threads }}
           TULLIO_TEST_GROUP: ${{ matrix.group }}
-      - uses: actions/checkout@v2        #
-      - name: Setup tmate session        #
-        uses: mxschmitt/action-tmate@v3  # https://github.com/marketplace/actions/debugging-with-tmate
-        timeout-minutes: 120             #
       - uses: julia-actions/julia-processcoverage@v1
       - uses: codecov/codecov-action@v1
         with:

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
           - ubuntu-latest
         threads:
           - '1'
-          # - '6' # t>2 might be ignored on Julia <= 1.5
+          - '6' # t>2 might be ignored on Julia <= 1.5
         version:
           - '1.5'
           - '1' # automatically expands to the latest stable 1.x release of Julia