ci: Install only the required nix tools

A previous commit allowed to select each tool separately on the toolbox.

This commit makes use of that for CI to possibly speed up loading from cachix
a little bit. It will also cause fewer cache misses when nix code is changed.

Resolves #3183

.github/workflows/docs.yaml

@@ -32,7 +32,7 @@ jobs:
       uses: ./.github/actions/setup-nix
       with:
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-        tools: docs
+        tools: docs.build.bin
     - run: postgrest-docs-build
     - run: git diff --exit-code HEAD locales || echo "Please commit changes to the locales/ folder after running postgrest-docs-build."
 
@@ -46,7 +46,7 @@ jobs:
       uses: ./.github/actions/setup-nix
       with:
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-        tools: docs
+        tools: docs.spellcheck.bin docs.dictcheck.bin
     - name: Run spellcheck
       run: postgrest-docs-spellcheck
     - name: Run dictcheck
@@ -63,5 +63,5 @@ jobs:
       uses: ./.github/actions/setup-nix
       with:
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-        tools: docs
+        tools: docs.linkcheck.bin
     - run: postgrest-docs-linkcheck