devel/jujutsu: fix build on big-endian architectures

While functions for converting to LE are suffixed _le, functions for converting to BE don't have any suffix:
error[E0599]: no method named put_i16_be found for struct Vec<u8> in the current scope

--> /wrkdirs/usr/ports/devel/jujutsu/work/jj-0.19.0/cargo-crates/serde_bser-0.4.0/src/ser/mod.rs:136:22
 |

136 | self.scratch.put_i16_be(v);

|                      ^^^^^^^^^^
|

help: there is a method put_i16_le with a similar name

|

136 | self.scratch.put_i16_le(v);

|                      ~~~~~~~~~~

error[E0599]: no method named put_i32_be found for struct Vec<u8> in the current scope