Regenerate haskell-ci workflow using 0.12.1

Instead of using an unreleased version, stick to what we have in nixpkgs
to make maintenance simpler.

.github/workflows/haskell-ci.yml

@@ -8,9 +8,9 @@
 #
 # For more information, see https://github.com/haskell-CI/haskell-ci
 #
-# version: 0.13.20210525
+# version: 0.12.1
 #
-# REGENDATA ("0.13.20210525",["--doctest","--doctest-version=>0.18","--doctest-options=-i ../../dist-newstyle/build/*/*/distribution-nixpkgs-*/build/autogen","--hlint","github","distribution-nixpkgs.cabal"])
+# REGENDATA ("0.12.1",["--doctest","--doctest-version=>0.18","--doctest-options=-i ../../dist-newstyle/build/*/*/distribution-nixpkgs-*/build/autogen","--hlint","github","distribution-nixpkgs.cabal"])
 #
 name: Haskell-CI
 on:
@@ -21,7 +21,7 @@ jobs:
     name: Haskell-CI - Linux - ${{ matrix.compiler }}
     runs-on: ubuntu-18.04
     container:
-      image: buildpack-deps:bionic
+      image: buildpack-deps:xenial
     continue-on-error: ${{ matrix.allow-failure }}
     strategy:
       matrix:
@@ -114,7 +114,7 @@ jobs:
           cabal-plan --version
       - name: install doctest
         run: |
-          $CABAL --store-dir=$HOME/.haskell-ci-tools/store v2-install $ARG_COMPILER --ignore-project -j2 doctest --constraint='doctest >0.18'
+          $CABAL --store-dir=$HOME/.haskell-ci-tools/store v2-install $ARG_COMPILER --ignore-project -j2 doctest --constraint='doctest ^>=0.17'
           doctest --version
       - name: install hlint
         run: |
@@ -179,10 +179,10 @@ jobs:
       - name: doctest
         run: |
           cd ${PKGDIR_distribution_nixpkgs} || false
-          doctest -i ../../dist-newstyle/build/*/*/distribution-nixpkgs-*/build/autogen -XMonadFailDesugaring src
+          doctest -i ../../dist-newstyle/build/*/*/distribution-nixpkgs-*/build/autogen src
       - name: hlint
         run: |
-          if [ $((HCNUMVER >= 90000)) -ne 0 ] ; then (cd ${PKGDIR_distribution_nixpkgs} && hlint -XMonadFailDesugaring src) ; fi
+          if [ $((HCNUMVER >= 90000)) -ne 0 ] ; then (cd ${PKGDIR_distribution_nixpkgs} && hlint src) ; fi
       - name: cabal check
         run: |
           cd ${PKGDIR_distribution_nixpkgs} || false