docs(solidity-resources): drop dead LearnWeb3 link - #74

A clean, well-evidenced 2-line docs removal of a dead LearnWeb3 link from evm/solidity-resources.mdx, with sound reasoning for leaving the VS Code Marketplace link untouched. No correctness, security, or style issues; the only notes are the stale copy in the generated llms-full.txt (self-resolving) and the fact that both second-opinion review passes produced no output.