patch 8.1.2243: typos in comments

Problem:    Typos in comments.
Solution:   Fix the typos. (Dominique Pelle, closes #5160)  Also adjust
            formatting a bit.
diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index 0712f4e..685a6d7 100644
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -3213,7 +3213,7 @@
 
     if (nfa_calc_size == FALSE)
     {
-	// Allocate space for the stack. Max states on the stack: "nstate'.
+	// Allocate space for the stack. Max states on the stack: "nstate".
 	stack = ALLOC_MULT(Frag_T, nstate + 1);
 	if (stack == NULL)
 	    return NULL;