fix(coverage): remove work-around for implicit `else`

[AriPerkkio]

Description

• Upstream fix for istanbul-lib-source-maps was fixed and released, let's remove our patch
• Ref. https://github.com/istanbuljs/istanbuljs/pull/706
• Ref. https://github.com/vitest-dev/vitest/pull/2275

Test case:

https://github.com/vitest-dev/vitest/blob/b1a27d40493301f7b135b6ba99d52c9edc28fffb/test/coverage-test/test/implicit-else.istanbul.test.ts#L5-L20

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[AriPerkkio]

Updating istanbul-lib-source-maps breaks other coverage tests 🤔

[AriPerkkio]

Another upstream fix set up in https://github.com/istanbuljs/istanbuljs/pull/789