update MSRV to 1.74

Motivation here is to be able to uprade to the latest `kstring`
which requires v1.73 as minimum version.

It's probably fair just to go as high as possible, as long
as `helix` is fine with it which also needs 1.74 right now.

Author: Byron

.github/workflows/msrv.yml

@@ -21,7 +21,7 @@ jobs:
     env:
       # dictated by `firefox` to support the `helix` editor, but now probably effectively be controlled by `jiff`, which also aligns with `regex`.
       # IMPORTANT: adjust etc/msrv-badge.svg as well
-      rust_version: 1.70.0
+      rust_version: 1.74.0
     steps:
       - uses: actions/checkout@v4
       - uses: extractions/setup-just@v2