Fix T88635: VSE: Select Linked gives unpredictable results

Caused by {rB66923031e6f2}.

Code would process unselected sequences and skip selected, needs to be
the other way around.

Maniphest Tasks: T88635

Differential Revision: https://developer.blender.org/D11424

source/blender/editors/space_sequencer/sequencer_select.c

@@ -808,7 +808,7 @@ static bool select_linked_internal(Scene *scene)
   bool changed = false;
 
   LISTBASE_FOREACH (Sequence *, seq, SEQ_active_seqbase_get(ed)) {
-    if ((seq->flag & SELECT) != 0) {
+    if ((seq->flag & SELECT) == 0) {
       continue;
     }
     /* Only get unselected neighbors. */