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/vim9.h b/src/vim9.h
index a79ffb5..d2c23be 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -703,7 +703,7 @@
 
     garray_T	ctx_locals;	    // currently visible local variables
 
-    int		ctx_has_closure;    // set to one if a closures was created in
+    int		ctx_has_closure;    // set to one if a closure was created in
 				    // the function
 
     garray_T	ctx_imports;	    // imported items