Use lazy capture pattern in asset checker

[aduth]

Why: To fix an issue where if there's another occurrence of a quote within the same line as a matched asset path, the path would wrongly include the text up to the last occurrence of a quote in the line.

You can see this on master:

$ make check_asset_strings 
find ./app/javascript -name "*.js*" | xargs ./scripts/check-assets
./app/javascript/app/document-capture/components/full-screen.jsx
Missing asset, close-white-alt.svg" className="full-screen-close-icon
make: *** [check_asset_strings] Error 1

With these changes, the misidentified error above should no longer be reported.

Reference:

• https://www.rexegg.com/regex-quantifiers.html#lazy_solution

[ironman5366]

LGTM