Fix iframe width

[fiskus]

• Changelog entry (skip if change is not significant to end users, e.g. docs only)

[codecov]

Codecov Report

Merging #3279 (a035632) into master (010115a) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #3279   +/-   ##
=======================================
  Coverage   35.29%   35.29%           
=======================================
  Files         666      666           
  Lines       29237    29237           
  Branches     4325     4325           
=======================================
  Hits        10320    10320           
  Misses      17727    17727           
  Partials     1190     1190           

Flag	Coverage Δ
api-python	90.79% <ø> (ø)
catalog	8.86% <0.00%> (ø)
lambda	86.05% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...atalog/app/components/Preview/renderers/IFrame.tsx	0.00% <ø> (ø)
...alog/app/containers/Admin/Settings/ThemeEditor.tsx	0.00% <0.00%> (ø)

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