Fix edit link on docs/examples

[ngyikp]

Right now, the Edit link on https://storybook.js.org/testing/structural-testing/ is pointing to an invalid link at https://github.com/storybooks/storybook/tree/master/docs/pages/testing/structural-testing/index.md
The correct link is https://github.com/storybooks/storybook/blob/master/docs/src/pages/testing/structural-testing/index.md

The examples page also have a similar problem.

What I did

Change the strings to point to the valid link.

How to test

Build the documentation and test the edit links.

[codecov]

Codecov Report

Merging #2396 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2396   +/-   ##
=======================================
  Coverage   19.92%   19.92%           
=======================================
  Files         293      293           
  Lines        6485     6485           
  Branches      763      756    -7     
=======================================
  Hits         1292     1292           
- Misses       4599     4604    +5     
+ Partials      594      589    -5

Impacted Files	Coverage Δ
app/vue/src/server/config/babel.js	0% <0%> (-100%)	⬇️
app/vue/src/server/babel_config.js	0% <0%> (-77.42%)	⬇️
app/react/src/server/utils.js	0% <0%> (-53.58%)	⬇️
addons/info/src/components/markdown/code.js	24.13% <0%> (ø)	⬆️
.../src/manager/containers/CommentsPanel/dataStore.js	34.04% <0%> (ø)	⬆️
addons/jest/src/components/PanelTitle.js	0% <0%> (ø)	⬆️
app/react-native/src/bin/storybook-start.js	0% <0%> (ø)	⬆️
addons/knobs/src/components/types/Object.js	5.88% <0%> (ø)	⬆️
addons/info/src/components/PropTable.js	21.36% <0%> (ø)	⬆️
addons/jest/src/components/Indicator.js	0% <0%> (ø)	⬆️
... and 30 more

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[Hypnosphi]

Great, thanks!