update: fetch latest Geckodriver via GH api

Correct typo in syntax

Author: VietND96

NodeFirefox/Dockerfile

@@ -31,7 +31,7 @@ RUN if [ "$(dpkg --print-architecture)" = "amd64" ]; then \
 # GeckoDriver
 #============
 ARG GECKODRIVER_VERSION=latest
-RUN if LATEST_VERSION=$(curl -s https://api.github.com/repos/mozilla/geckodriver/releases/latest | jq -r '.tag_name') \
+RUN LATEST_VERSION=$(curl -s https://api.github.com/repos/mozilla/geckodriver/releases/latest | jq -r '.tag_name') \
   && DRIVER_ARCH=$(if [ "$(dpkg --print-architecture)" = "amd64" ]; then echo "linux64"; else echo "linux-aarch64"; fi) \
   && GK_VERSION=$(if [ ${GECKODRIVER_VERSION:-latest} = "latest" ]; then echo "${LATEST_VERSION}"; else echo $GECKODRIVER_VERSION; fi) \
   && echo "Using GeckoDriver version: "$GK_VERSION \