Fix Plan View duplicate scrollbars (#6865)

* Closes #6864
- CSS fixes to remove problematic duplicate overflow handling.

* fix(e2e): stabilize autoscale test

* fix(e2e): mark overlay plot tagging test as slow

* fix(e2e): stabilize ITC e2e test

* fix(e2e): don't use hard wait

* fix: remove .only 😳

---------

Co-authored-by: Jesse Mazzella <jesse.d.mazzella@nasa.gov>
Co-authored-by: Jesse Mazzella <ozyx@users.noreply.github.com>

src/plugins/timeline/timeline.scss

@@ -2,11 +2,6 @@
   overflow: hidden;
 }
 
-.c-plan.c-timeline-holder {
-  overflow-x: hidden;
-  overflow-y: auto;
-}
-
 .c-timeline__objects {
   display: contents;
 }