'Could not find apksig-7.1.3.jar in android studio

I'm trying to sync build.gradle for a flutter app in android studio but it gave this error

this error comes after I tried solving "ssl peer shut down incorrectly" error using the first answer in this question .

I followed all three steps of that solution but without adding the certificates and then I reconverted the steps but I remained with the same error.

Then I was trying to upgrade the gradle but it was interuppted and then the above error occured.

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