CI: cabal-plan allow-newer for GHC 9.6 (TODO: revert)

Author: ulysses4ever

.github/workflows/validate.yml

@@ -97,7 +97,7 @@ jobs:
       - name: Install cabal-plan
         run: |
           cd $(mktemp -d)
-          cabal install cabal-plan --constraint='cabal-plan +exe'
+          cabal install cabal-plan --allow-newer="base,ghc-prim,template-haskell" --constraint='cabal-plan +exe'
           echo "$HOME/.cabal/bin" >> $GITHUB_PATH
 
       # The tool is not essential to the rest of the test suite. If
@@ -251,7 +251,7 @@ jobs:
       - name: Install cabal-plan
         run: |
           cd $(mktemp -d)
-          cabal install cabal-plan --constraint='cabal-plan +exe' --allow-newer
+          cabal install cabal-plan --allow-newer="base,ghc-prim,template-haskell" --constraint='cabal-plan +exe' --allow-newer
           echo "$HOME/.cabal/bin" >> $GITHUB_PATH
 
       # The tool is not essential to the rest of the test suite. If
@@ -373,7 +373,7 @@ jobs:
       - name: Install cabal-plan
         run: |
           cd $(mktemp -d)
-          cabal install cabal-plan --constraint='cabal-plan +exe'
+          cabal install cabal-plan --allow-newer="base,ghc-prim,template-haskell" --constraint='cabal-plan +exe'
           echo "$HOME/.cabal/bin" >> $GITHUB_PATH
 
       - name: Validate build
@@ -421,7 +421,7 @@ jobs:
       - name: Install cabal-plan
         run: |
           cd $(mktemp -d)
-          cabal install cabal-plan --constraint='cabal-plan +exe'
+          cabal install cabal-plan --allow-newer="base,ghc-prim,template-haskell" --constraint='cabal-plan +exe'
           echo "$HOME/.cabal/bin" >> $GITHUB_PATH
 
       - name: Download cabal executable from workflow artifacts