Update dependency firebase to v4.1.4

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This PR contains the following updates:

Package	Type	Update	Change
firebase (source, changelog)	dependencies	patch	4.1.3 -> 4.1.4

By merging this PR, the issue #81 will be automatically resolved and closed:

Severity	CVSS Score	CVE
High	8.8	CVE-2018-3728
High	7.1	WS-2018-0096

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Release Notes

firebase/firebase-js-sdk

v4.1.4: 4.1.4

Compare Source

Improvements

• Refactored internal implementation of database to TypeScript. #​72 and #​66 (Thanks to @​schmidt-sebastian, @​mikelehen and @​jsayol for their help in this!)
• Bundle size improvements for firebase-app.js, firebase-storage.js,
  firebase-messaging.js. #​94 (Shout out to @​jsayol for this PR!)

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• If you want to rebase/retry this PR, check this box

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⚠ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: yarn.lock

No /opt/buildpack/tools/yarn-slim/1.22.19/bin/yarn defined - aborting