No need to log out and back in fix

CROSS_COMPILE.md

@@ -1,13 +1,10 @@
 Install docker:
-
+```
 $ sudo apt install docker
 $ sudo usermod -aG docker $USER
-
-Then log out and back in.
-
+$ exec sudo su -l $USER
 $ sudo systemctl start docker
-
 $ cargo install cross
 $ cross build --release --features tls_vendored --target armv7-unknown-linux-musleabihf
-
+```
 The cross-compiled binary is at target/armv7-unknown-linux-musleabihf/release/conduit