docs: Improve Grammar and Clarity in verify-smart-contract.mdx

[0xwitty]

I noticed a few issues in the documentation that could use some refinement for clarity and grammatical accuracy. Here's what I've addressed:

1. "Enter in the contract address"

   • The phrase "Enter in" is redundant. It's been simplified to "Enter the contract address" for correctness and conciseness.

2. "sourcecode"

   • In the "Troubleshooting" section, "sourcecode" is written as one word. Corrected it to "source code" to align with standard usage.

3. "File should follows solidity format"

   • Found a grammatical error in the "Solidity (Standard JSON input)" section. Changed it to "File should follow the Solidity format" for proper subject-verb agreement and clarity.

Happy New Year!