runtime(doc): Fix typos in several documents (#13420)

* Fix typos in several documents
* Update runtime/doc/terminal.txt

Co-authored-by: K.Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/terminal.txt b/runtime/doc/terminal.txt
index 62bc6e6..70cfd7f 100644
--- a/runtime/doc/terminal.txt
+++ b/runtime/doc/terminal.txt
@@ -1485,8 +1485,9 @@
 Any value greater than 1 will set the Asm window height to that value.
 
 						*termdebug_variables_window*
-If you want the Var window shown by default, set the flag to 1.
-the "variables_window_height" entry can be used to set the window height: >
+If you want the Var window shown by default, set the "variables_window" flag
+to 1.  The "variables_window_height" entry can be used to set the window
+height: >
 	let g:termdebug_config['variables_window'] = 1
 	let g:termdebug_config['variables_window_height'] = 15
 If there is no g:termdebug_config you can use: >