Bump logger from 1.6.3 to 1.6.4 in /steep

Bumps [logger](https://github.com/ruby/logger) from 1.6.3 to 1.6.4.
- [Release notes](https://github.com/ruby/logger/releases)
- [Commits](ruby/logger@v1.6.3...v1.6.4)

---
updated-dependencies:
- dependency-name: logger
  dependency-type: indirect
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

steep/Gemfile.lock

@@ -31,7 +31,7 @@ GEM
     listen (3.9.0)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
-    logger (1.6.3)
+    logger (1.6.4)
     minitest (5.25.4)
     parser (3.3.6.0)
       ast (~> 2.4.1)