Remove unused import

Author: lauzadis

runtime/auth/aws-signing-default/common/src/aws/smithy/kotlin/runtime/auth/awssigning/Canonicalizer.kt

@@ -20,7 +20,6 @@ import aws.smithy.kotlin.runtime.text.encoding.Encodable
 import aws.smithy.kotlin.runtime.text.encoding.PercentEncoding
 import aws.smithy.kotlin.runtime.text.encoding.encodeToHex
 import aws.smithy.kotlin.runtime.time.TimestampFormat
-import kotlinx.coroutines.IO
 import kotlinx.coroutines.withContext
 
 /**