Merge pull request #3639 from AritraDey-Dev/fix/dev-intro.md

BUG: DEV-INTRO.md

Author: robkooper

DEV-INTRO.md

@@ -42,7 +42,7 @@ _Note for Linux (including Windows WSL2) users:_ add your user to the docker gro
 
 ```sh
 # for linux users
-sudo adduser ${USER} docker.
+sudo adduser ${USER} docker
 ```
 
 ### Deploying PEcAn in Docker