patch 8.2.1015: popup filter gets key with modifier prepended

Problem:    Popup filter gets key with modifier prepended when using
            modifyOtherKeys.
Solution:   Remove the shift modifier when it is included in the key, also
            when the Alt or Meta modifier is used.
diff --git a/src/term.c b/src/term.c
index c4ca33e..1556c2e 100644
--- a/src/term.c
+++ b/src/term.c
@@ -4772,11 +4772,14 @@
     // Some keys already have Shift included, pass them as
     // normal keys.  Not when Ctrl is also used, because <C-H>
     // and <C-S-H> are different.
-    if (modifiers == MOD_MASK_SHIFT
+    // Also for <A-S-a> and <M-S-a>.
+    if ((modifiers == MOD_MASK_SHIFT
+		|| modifiers == (MOD_MASK_SHIFT | MOD_MASK_ALT)
+		|| modifiers == (MOD_MASK_SHIFT | MOD_MASK_META))
 	    && ((key >= '@' && key <= 'Z')
 		|| key == '^' || key == '_'
 		|| (key >= '{' && key <= '~')))
-	modifiers = 0;
+	modifiers &= ~MOD_MASK_SHIFT;
 
     // When used with Ctrl we always make a letter upper case,
     // so that mapping <C-H> and <C-h> are the same.  Typing