fix: modal exit redirect

[KristinAoki]

This PR fixes the Custom Page modal not closing on cancel and on close not removing /editor from the url.

Testing

1. Navigate to the custom pages.
2. Click the pencil icon to edit a page.
3. Click cancel.
4. Modal should close.
5. Footer and header should display as expected.
6. Edit the same page.
7. Make some edits.
8. Click Save.
9. Modal should close.
10. Footer and header should display as expected.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (221fcf7) 86.67% compared to head (64e2d51) 86.66%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #659      +/-   ##
==========================================
- Coverage   86.67%   86.66%   -0.01%     
==========================================
  Files         389      389              
  Lines        5799     5797       -2     
  Branches     1274     1274              
==========================================
- Hits         5026     5024       -2     
  Misses        748      748              
  Partials       25       25              

Files	Coverage Δ
src/custom-pages/CustomPages.jsx	82.05% <0.00%> (-0.88%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.