Missed double quote fix

docs/sources/installation/docker.md

@@ -24,7 +24,7 @@ container:
 
     $ docker run -d -p 3000:3000 \
         -v /var/lib/grafana:/var/lib/grafana \
-        -e "GF_SECURITY_ADMIN_PASSWORD=secret  \
+        -e "GF_SECURITY_ADMIN_PASSWORD=secret" \
         grafana/grafana:develop
 
 In the above example I map the data folder and sets a configuration option via