Remove LP_ENABLE_VCSH

This option was added along with the VCSH prompt mark, but it never did
anything. It still doesn't today, so it is being removed.

It was also never mentioned in documentation, so I doubt most people
know about it.

liquidprompt

@@ -209,7 +209,6 @@ __lp_source_config() {
     LP_ENABLE_BATT=${LP_ENABLE_BATT:-1}
     LP_ENABLE_GIT=${LP_ENABLE_GIT:-1}
     LP_ENABLE_SVN=${LP_ENABLE_SVN:-1}
-    LP_ENABLE_VCSH=${LP_ENABLE_VCSH:-1}
     LP_ENABLE_FOSSIL=${LP_ENABLE_FOSSIL:-1}
     LP_ENABLE_HG=${LP_ENABLE_HG:-1}
     LP_ENABLE_BZR=${LP_ENABLE_BZR:-1}