Change to CANONICAL_LENGTH in std/testing/mock.rs

[LeTurt333]

Carried over from Discord

// cosmwasm-std/src/testing/mock.rs | line 81
const CANONICAL_LENGTH: usize = 54;

causes issues in tests when a human readable contract address is passed to addr_validate in the contracts core logic

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Example with Juno addresses:

usize of a human readable Juno wallet address = 43 ✅

usize of a human readable Juno contract address = 63 ❌

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Increasing this to something that supports contract addresses makes sense, perhaps 100 to support chains with longer prefixes