Remove nonsense feature gating

This feature gating is nonsense, I wrote it in commit:
`cbee9781e8 Move unit types to units` before I understood that
`std::string::String` is a re-export of `alloc::string::String`.

Remove the nonsense feature gating. This patch has zero effect on the
logic.

Author: tcharding

units/src/parse.rs

@@ -149,10 +149,9 @@ macro_rules! impl_tryfrom_str_from_int_infallible {
 #[macro_export]
 macro_rules! impl_parse_str_from_int_infallible {
     ($to:ident, $inner:ident, $fn:ident) => {
-        #[cfg(all(feature = "alloc", not(feature = "std")))]
-        $crate::impl_tryfrom_str_from_int_infallible!(&str, $to, $inner, $fn; alloc::string::String, $to, $inner, $fn; alloc::boxed::Box<str>, $to, $inner, $fn);
-        #[cfg(feature = "std")]
-        $crate::impl_tryfrom_str_from_int_infallible!(&str, $to, $inner, $fn; std::string::String, $to, $inner, $fn; std::boxed::Box<str>, $to, $inner, $fn);
+        $crate::impl_tryfrom_str_from_int_infallible!(&str, $to, $inner, $fn);
+        #[cfg(feature = "alloc")]
+        $crate::impl_tryfrom_str_from_int_infallible!(alloc::string::String, $to, $inner, $fn; alloc::boxed::Box<str>, $to, $inner, $fn);
 
         impl core::str::FromStr for $to {
             type Err = $crate::parse::ParseIntError;