Update ubuntu.md

Author: imba-tjd

install/linux/docker-ce/ubuntu.md

@@ -42,7 +42,7 @@ Docker Engine - Community is supported on `x86_64` (or `amd64`), `armhf`, `arm64
 
 ### Uninstall old versions
 
-Older versions of Docker were called `docker`, `docker.io `, or `docker-engine`.
+Older versions of Docker were called `docker`, `docker.io`, or `docker-engine`.
 If these are installed, uninstall them:
 
 ```bash