fix: use modern bash command substitution

- backticks command substitution is deprecated

Author: fioan89

.github/workflows/build.yml

@@ -86,7 +86,7 @@ jobs:
         shell: bash
         run: |
           cd ${{ github.workspace }}/build/distributions
-          FILENAME=`ls *.zip`
+          FILENAME=$(ls *.zip)
           unzip "$FILENAME" -d content
           echo "filename=${FILENAME:0:-4}" >> $GITHUB_OUTPUT