update status of tests

Manual_tests.md

@@ -18,13 +18,13 @@ Panning:
     short node entirely within viewer, cursor in middle of screen
     ✓ arrow keys
     ✓ page-up positions cursor on top line
-    x page-down positions cursor on bottom line
+    ✓ page-down positions cursor on bottom line
     ✓ mouse panning
     tall node extending below viewport
-    x repeated down arrow near bottom pans down
+    ✓ repeated down arrow near bottom pans down
     ✓ repeated up arrow
     ✓ repeated down arrow
-    x repeated pagedown
+    ✓ repeated pagedown
     ✓ repeated pageup
     ✓ mouse panning
     tall node extending above viewport