fix(pghero): update because CVE-2023-22626 (#23190)

There is a vulnerability
[CVE-2023-22626](https://github.com/advisories/GHSA-vf99-xw26-86g5)

```
Name: pghero
Version: 2.8.3
CVE: CVE-2023-22626
GHSA: GHSA-vf99-xw26-86g5
Criticality: High
URL: https://github.com/ankane/pghero/issues/439
Title: Information Disclosure Through EXPLAIN Feature
Solution: upgrade to '>= 3.1.0'
```

Gemfile

@@ -15,7 +15,7 @@ gem 'rack', '~> 2.2.6'
 gem 'hamlit-rails', '~> 0.2'
 gem 'pg', '~> 1.4'
 gem 'makara', '~> 0.5'
-gem 'pghero', '~> 2.8'
+gem 'pghero'
 gem 'dotenv-rails', '~> 2.8'
 
 gem 'aws-sdk-s3', '~> 1.117', require: false