options: Fix a typo in docs of unsafe_tactic_exec
options: Fix a typo in docs of unsafe_tactic_exec

Suggested-By: da39a3ee5e6b4b0d3255bfef95601890afd80709@msprotz

FStarLang/FStar,A-Manning/FStar,FStarLang/FStar,A-Manning/FStar,A-Manning/FStar,FStarLang/FStar