fix(core, windows): remove unused map of string that was causing a crash

[Lyokone]

Description

Before we used a STATIC compilation of the different Windows plugins, we needed to recreate the Firebase App in each plugin. I've removed this stale code that we don't use anymore.

Related Issues

closes #11684

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Breaking Change

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[P-ro-VL]

This pull is really helpful. I tried to delete some lines of code like this and everything worked normally.