Use is_none()

Clippy emits:

 warning: binary comparison to literal `Option::None`

As suggested, use `find.is_none()` instead of comparison with `None`.

bitcoin/src/blockdata/transaction.rs

@@ -165,7 +165,7 @@ impl core::str::FromStr for OutPoint {
             return Err(ParseOutPointError::TooLong);
         }
         let find = s.find(':');
-        if find == None || find != s.rfind(':') {
+        if find.is_none() || find != s.rfind(':') {
             return Err(ParseOutPointError::Format);
         }
         let colon = find.unwrap();