Cleanup redundant paths in the ExampleNFT

[SupunS]

Description

Noticed there are redundant path variables for the collection-path, so removed the local ones, which were leftovers from the previous update in https://github.com/onflow/flow-nft/pull/205.

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For contributor use:

• [x] Targeted PR against master branch
• [ ] Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• [x] Code follows the standards mentioned here.
• [ ] Updated relevant documentation
• [x] Re-reviewed Files changed in the Github PR explorer
• [x] Added appropriate labels
• [ ] Update the version in package.json when there is a change in the smart contracts