fixed action.yml

Author: goergisn

action.yml

@@ -17,7 +17,7 @@ runs:
       run: |
         git clone https://github.com/Adyen/adyen-swift-public-api-diff ./tmp-diff-checkout
         cd ./tmp-diff-checkout
-        LATEST_VERSION = $(git describe --abbrev=0 --tags)
+        LATEST_VERSION=$(git describe --abbrev=0 --tags)
         cd ..
         echo $LATEST_VERSION