cmd/compile: fix spelling error

Change-Id: Ifc533ee98a7684060d20340087c1b29f722ae46b
Reviewed-on: https://go-review.googlesource.com/84835Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/pgen.go

@@ -599,7 +599,7 @@ func preInliningDcls(fnsym *obj.LSym) []*Node {
 	}
 	for _, n := range dcl {
 		c := n.Sym.Name[0]
-		// Avoid reporting "_" parameters, since if there are more tham
+		// Avoid reporting "_" parameters, since if there are more than
 		// one, it can result in a collision later on, as in #23179.
 		if unversion(n.Sym.Name) == "_" || c == '.' || n.Type.IsUntyped() {
 			continue