fix(deps): update dependency firebase_core to v4

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
firebase_core (source)	dependencies	major	^3.4.0 → 4.3.0

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Release Notes

firebase/flutterfire (firebase_core)

v4.3.0

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• FEAT: bump Firebase iOS SDK to 12.6.0 (#​17857). (668331b4)

v4.2.1

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• Update a dependency to the latest release.

v4.2.0

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• FIX: a bug with the demoProjectId arg to Firebase.initializeApp() (#​17703). (09d03aac)
• FEAT: bump Android SDK to version 34.4.0 (#​17786). (3edfc18d)
• FEAT: bump Firebase iOS SDK to 12.4.0 (#​17779). (51ed3fbb)

v4.1.1

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• Update a dependency to the latest release.

v4.1.0

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• FEAT: bump Firebase iOS SDK to 12.2.0 (#​17677). (ecd8889d)
• FEAT: bump Firebase android SDK to 34.1.0 (#​17668). (2af66ab3)

v4.0.0

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Note: This release has breaking changes.

• BREAKING FEAT: bump iOS SDK to version 12.0.0 (#​17549). (b2619e68)
• BREAKING FEAT: bump Android SDK to version 34.0.0 (#​17554). (a5bdc051)

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