lang/mlkit: update to 4.7.5

Changelog: https://github.com/melsman/mlkit/blob/master/NEWS.md

• ReML released as part of the distribution
• Improved documentation of basis library
• Addition of IEEE_REAL signature and IEEEReal structure. Improved Real support.
• Initial support for explicit region and effect annotations, including constraints on function invocations. The modified source language, which we call ReML (a Standard ML program is also a ReML program) is enabled with the -er flag
• Generate position-independent machine code

PR: 274695