patch 8.2.2236: 'scroll' option can change when setting the statusline

Problem:    'scroll' option can change when setting the statusline or tabline
            but the option context is not updated.
Solution:   Update the script context when the scroll option is changed as a
            side effect. (Christian Brabandt, closes #7533)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index db62f8a..4d26df8 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -6321,7 +6321,9 @@
 			local to window
 	Number of lines to scroll with CTRL-U and CTRL-D commands.  Will be
 	set to half the number of lines in the window when the window size
-	changes.  If you give a count to the CTRL-U or CTRL-D command it will
+	changes.  This may happen when enabling the |status-line| or
+	'tabline' option after setting the 'scroll' option.
+	If you give a count to the CTRL-U or CTRL-D command it will
 	be used as the new value for 'scroll'.  Reset to half the window
 	height with ":set scroll=0".