fix(flagpole-schema): Update created at schema pattern to accept UTC format

[nikkikapadia]

This updates the sentry repo to adopt this fix from the options repo. It accepts the UTC datetime format in the created_at field in flagpole feature flags.

[codecov]

Bundle Report

Changes will increase total bundle size by 29.24MB (100.0%) ⬆️⚠️, exceeding the configured threshold of 5%.

Bundle name	Size	Change
app-webpack-bundle-array-push	29.24MB	29.24MB (100%) ⬆️⚠️

[getsantry]

This pull request has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you add the label WIP, I will leave it alone unless WIP is removed ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[getsantry]

This pull request has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you add the label WIP, I will leave it alone unless WIP is removed ... forever!

---

"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[getsantry]

This pull request has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you add the label WIP, I will leave it alone unless WIP is removed ... forever!

---

"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀