Remove From<ParseIntError>

The errors in `units::locktime::absolute` are complex, I'd like to make
them more simple so they are more understandable.

I have no clue why this is implemented - remove it.

units/src/locktime/absolute.rs

@@ -10,7 +10,6 @@ use internals::write_err;
 
 #[cfg(feature = "alloc")]
 use crate::parse;
-use crate::parse::ParseIntError;
 
 /// The Threshold for deciding whether a lock time value is a height or a time (see [Bitcoin Core]).
 ///
@@ -360,12 +359,6 @@ impl ParseError {
     }
 }
 
-impl From<ParseIntError> for ParseError {
-    fn from(value: ParseIntError) -> Self {
-        Self::InvalidInteger { source: value.source, input: value.input }
-    }
-}
-
 impl From<ConversionError> for ParseError {
     fn from(value: ConversionError) -> Self { Self::Conversion(value.input.into()) }
 }