fix syntax

Author: blink1073

.github/workflows/build.yml

@@ -57,7 +57,7 @@ jobs:
           jupyter labextension develop . --overwrite
 
       - name: Check docs can be build + links
-        if: {{ matrix.os == 'ubuntu-latest' }}
+        if: ${{ matrix.os == 'ubuntu-latest' }}
         working-directory: jupyter-widget-testwidgets/docs
         run: |
           sudo apt install -y pandoc

{{cookiecutter.github_project_name}}/.github/workflows/build.yml

@@ -32,7 +32,7 @@ jobs:
           yarn run test
 
       - name: Check docs can be build + links
-        if: {{ matrix.os == 'ubuntu-latest' }}
+        if: ${{ matrix.os == 'ubuntu-latest' }}
         run: |
           sudo apt install -y pandoc
           pushd docs