Bump securerandom from 0.3.2 to 0.4.0 in /steep

Bumps [securerandom](https://github.com/ruby/securerandom) from 0.3.2 to 0.4.0.
- [Release notes](https://github.com/ruby/securerandom/releases)
- [Commits](ruby/securerandom@v0.3.2...v0.4.0)

---
updated-dependencies:
- dependency-name: securerandom
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

steep/Gemfile.lock

@@ -43,7 +43,7 @@ GEM
       ffi (~> 1.0)
     rbs (3.6.1)
       logger
-    securerandom (0.3.2)
+    securerandom (0.4.0)
     steep (1.8.3)
       activesupport (>= 5.1)
       concurrent-ruby (>= 1.1.10)