Fix issue faced at mint_nft tutorial

[EasonC13]

Description

I'm facing trouble when I go through instructions in NFT move-examples/mint_nft/4-Getting-Production-Ready

I fix and clarify them at this pull reuqestion.

First I update the path from aptos-core/aptos/move-e2e-tests/src/tests/mint_nft.rs to aptos-core/aptos-move/e2e-move-tests/src/tests/mint_nft.rs

Then I add the "Make sure you're in the right directory." instruction before running cargo test generate_nft_tutorial_part4_signature -- --nocapture

Finally, I fix a library import issue at aptos-core/aptos-move/e2e-move-tests/src/tests/mint_nft.rs. This issue makes me fail the test after edit the file according to the instruction.

Test Plan