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/memline.c b/src/memline.c
index 8772ad2..32cbb7e 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -2318,7 +2318,7 @@
 	ret = FALSE;
 
 #if defined(UNIX) || defined(MSWIN)
-    // process must known and not be running
+    // process must be known and not be running
     pid = char_to_long(b0.b0_pid);
     if (pid == 0L || mch_process_running(pid))
 	ret = FALSE;