Revert "Remove obsolete remote.NAME.timeout from config documentation"

Although the timeout setting is not explicitly read in the plugin's
implementation, it is actually used by JGit when pushing to the remote:

  tn.applyConfig(config);

so it was wrong to remove this documentation.  Add it back.

This reverts commit 10b903e488519a215dc0701c9e275745fbca5b9a.

Change-Id: I50892e73136b369ec5822b9d7039ad918e2f6d05