doc: add verb in front of command to run

Instead of using the command 'git clone' as a verb, use "run" as the
verb indicating the action of executing the command 'git clone'.

Signed-off-by: Kristoffer Haugsbakk <kristoffer.haugsbakk@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/gitcore-tutorial.txt

@@ -1478,7 +1478,7 @@ You can repack this private repository whenever you feel like.
 A recommended work cycle for a "subsystem maintainer" who works
 on that project and has an own "public repository" goes like this:
 
-1. Prepare your work repository, by 'git clone' the public
+1. Prepare your work repository, by running 'git clone' on the public
    repository of the "project lead". The URL used for the
    initial cloning is stored in the remote.origin.url
    configuration variable.