fix lints

ethers-etherscan/src/gas.rs

@@ -123,7 +123,7 @@ mod tests {
             assert!(oracle.fast_gas_price > 0);
             assert!(oracle.last_block > 0);
             assert!(oracle.suggested_base_fee > 0.0);
-            assert!(oracle.gas_used_ratio.len() > 0);
+            assert!(!oracle.gas_used_ratio.is_empty());
         })
         .await
     }

ethers-signers/src/ledger/app.rs

@@ -206,7 +206,7 @@ impl LedgerEthereum {
         let mut bytes = vec![depth as u8];
         for derivation_index in elements {
             let hardened = derivation_index.contains('\'');
-            let mut index = derivation_index.replace("'", "").parse::<u32>().unwrap();
+            let mut index = derivation_index.replace('\'', "").parse::<u32>().unwrap();
             if hardened {
                 index |= 0x80000000;
             }

ethers-solc/src/compile.rs

@@ -202,7 +202,7 @@ impl Solc {
     pub fn version_req(source: &Source) -> Result<VersionReq> {
         let version = utils::find_version_pragma(&source.content)
             .ok_or(SolcError::PragmaNotFound)?
-            .replace(" ", ",");
+            .replace(' ', ",");
 
         // Somehow, Solidity semver without an operator is considered to be "exact",
         // but lack of operator automatically marks the operator as Caret, so we need