fix: Fix incorrect validation in chanCloseFrozen function in README.md

[mdqst]

I noticed an issue in the chanCloseFrozen function where the validation abortTransactionUnless(hopsLength === 1) doesn't align with the intended logic.

Since this function is designed to handle multi-hop connections, the check should ensure that connectionHops length is greater than 1, not equal to 1.

This change ensures the function works correctly for its intended use case.