Switch CI to use ghc 8.8.3.

This should fix CI failures.

.github/workflows/ci.yml

@@ -51,7 +51,7 @@ jobs:
             cabal: '2.4'
           - ghc: '8.6.5'
             cabal: '2.4'
-          - ghc: '8.8.1'
+          - ghc: '8.8.3'
             cabal: '3.0'
           - ghc: '8.10.1'
             cabal: '3.2'

.github/workflows/nightly.yml

@@ -12,7 +12,7 @@ jobs:
     - uses: actions/checkout@v1
     - name: Install dependencies
       run: |
-          export PATH=/opt/cabal/3.0/bin:/opt/ghc/8.8.1/bin:$PATH
+          export PATH=/opt/cabal/3.0/bin:/opt/ghc/8.8.3/bin:$PATH
           ls /opt/cabal/*/bin
           ls /opt/ghc/*/bin
           ghc --version
@@ -21,7 +21,7 @@ jobs:
           cabal v2-build --dependencies-only . pandoc-citeproc
     - name: Build
       run: |
-          export PATH=/opt/cabal/3.0/bin:/opt/ghc/8.8.1/bin:$PATH
+          export PATH=/opt/cabal/3.0/bin:/opt/ghc/8.8.3/bin:$PATH
           cabal v2-install . pandoc-citeproc
           strip $HOME/.cabal/bin/pandoc
           strip $HOME/.cabal/bin/pandoc-citeproc