patch 8.2.3914: various spelling mistakes in comments

Problem:    Various spelling mistakes in comments.
Solution:   Fix the mistakes. (Dominique Pellé, closes #9416)
diff --git a/src/os_win32.c b/src/os_win32.c
index 7234fe8..b0ff1bb 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -2187,7 +2187,7 @@
 	}
     }
 
-    // Prepend single "." to pathext, it's means no extension added.
+    // Prepend single "." to pathext, it means no extension added.
     if (pathext == NULL)
 	pathext = (char_u *)".";
     else if (noext == TRUE)
@@ -7750,7 +7750,7 @@
 	// Now expand wildcards in the arguments.
 	// Temporarily add '(' and ')' to 'isfname'.  These are valid
 	// filename characters but are excluded from 'isfname' to make
-	// "gf" work on a file name in parenthesis (e.g.: see vim.h).
+	// "gf" work on a file name in parentheses (e.g.: see vim.h).
 	// Also, unset wildignore to not be influenced by this option.
 	// The arguments specified in command-line should be kept even if
 	// encoding options were changed.