fixed typo

Author: kubaneko

gcc/params.opt

@@ -426,7 +426,7 @@ The maximum number of instructions in an inner loop that is being considered for
 Common Joined UInteger Var(param_loop_versioning_max_outer_insns) Init(100) Param Optimization
 The maximum number of instructions in an outer loop that is being considered for versioning, on top of the instructions in inner loops.
 
--param=loop-versioning-histogram_prcnts=
+-param=loop-versioning-histogram_prcnt=
 Common Joined UInteger Var(param_loop_versioning_histogram_prcnt) Init(30) Param Optimization
 Percentage of the dominating iteration count required for versioning.