build: bump msrv to 1.60.0

the log crates requires this after Debian 12/bookworm released

.github/workflows/rust.yml

@@ -52,7 +52,7 @@ jobs:
           # Sometimes old rust versions don't yet have the lints (allow unknown) or don't have fixes in lints (false positives -> don't error, just warn).
           # When a certain distro is a target look up its version: https://repology.org/project/rust/versions
           - os: ubuntu-latest
-            toolchain: 1.56.1
+            toolchain: 1.60.0
             clippyargs: -A unknown-lints
             features: --all-features
     steps: