Upgrade GeckoDriver from 0.14.0 to 0.15.0

Author: elgalu

Dockerfile

@@ -572,8 +572,8 @@ USER root
 #============
 # GeckoDriver
 #============
-# Layer size: tiny: 4.088 MB
-ENV GECKOD_VER="0.14.0" \
+# Layer size: tiny: ~4 MB
+ENV GECKOD_VER="0.15.0" \
     GECKOD_URL="https://github.com/mozilla/geckodriver/releases/download"
 RUN wget --no-verbose -O geckodriver.tar.gz \
      "${GECKOD_URL}/v${GECKOD_VER}/geckodriver-v${GECKOD_VER}-linux64.tar.gz" \