chore(deps): update @sentry/browser to v5.21.1

[thi-bot]

This PR contains the following updates:

Package	Update	Type	Change
@sentry/browser	minor	devDependencies	5.20.1 -> 5.21.1

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Release Notes

getsentry/sentry-javascript

### [`v5.21.1`](https://togithub.com/getsentry/sentry-javascript/blob/master/CHANGELOG.md#​5211) [Compare Source](https://togithub.com/getsentry/sentry-javascript/compare/5.21.0...5.21.1) - [ember] fix: Make the package public and fix the build by bumping TypeScript to v3.9 - [eslint] test: Don't test eslint config/plugin on Node <= v8 ### [`v5.21.0`](https://togithub.com/getsentry/sentry-javascript/blob/master/CHANGELOG.md#​5210) [Compare Source](https://togithub.com/getsentry/sentry-javascript/compare/5.20.1...5.21.0) - [all] feat: Convert `sentry-javascript` to `ESLint` ([#​2786](https://togithub.com/getsentry/sentry-javascript/issues/2786)) - [internal/eslint] feat: Add `@sentry-internal/eslint-config-sdk` ([#​2807](https://togithub.com/getsentry/sentry-javascript/issues/2807)) - [internal/eslint] feat: Add `@sentry-internal/eslint-plugin-sdk` ([#​2807](https://togithub.com/getsentry/sentry-javascript/issues/2807)) - [ember] feat: Add `@sentry/ember` ([#​2739](https://togithub.com/getsentry/sentry-javascript/issues/2739)) - [angular] feat: Add `@sentry/angular` ([#​2787](https://togithub.com/getsentry/sentry-javascript/issues/2787)) - [react] feat: Add routing instrumentation for `React Router v4/v5` ([#​2780](https://togithub.com/getsentry/sentry-javascript/issues/2780)) - [gatsby] feat: support `process.env.SENTRY_RELEASE` ([#​2776](https://togithub.com/getsentry/sentry-javascript/issues/2776)) - [apm/tracing] feat: Export `addExtensionMethods` for SDKs to use ([#​2805](https://togithub.com/getsentry/sentry-javascript/issues/2805)) - [apm/tracing] ref: Remove `express` typing ([#​2803](https://togithub.com/getsentry/sentry-javascript/issues/2803)) - [node] fix: `Retry-After` header in node should be lower-case ([#​2779](https://togithub.com/getsentry/sentry-javascript/issues/2779))

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