Update gem_bench requirement from 2.0.3 to 2.0.5 in /benchmarks

Updates the requirements on [gem_bench](https://github.com/pboling/gem_bench) to permit the latest version.
- [Release notes](https://github.com/pboling/gem_bench/releases)
- [Changelog](https://github.com/pboling/gem_bench/blob/main/CHANGELOG.md)
- [Commits](pboling/gem_bench@v2.0.3...v2.0.5)

---
updated-dependencies:
- dependency-name: gem_bench
  dependency-type: direct:production
...

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

benchmarks/Gemfile

@@ -7,7 +7,7 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 ruby ">= 2.7.7"
 
 gem "benchmark-ips", "2.14.0"
-gem "gem_bench", "2.0.3"
+gem "gem_bench", "2.0.5"
 
 # NOTE: Regarding `require: false` below
 # 1. GitHub version of MemoWise and the local source of MemoWise share a namespace