Update dependency minitest-rails to v8

Author: renovate[bot]

Gemfile.lock

@@ -117,7 +117,6 @@ GEM
     bootsnap (1.18.6)
       msgpack (~> 1.2)
     builder (3.3.0)
-    cgi (0.5.0)
     climate_control (1.2.0)
     concurrent-ruby (1.3.5)
     connection_pool (2.5.3)
@@ -139,8 +138,7 @@ GEM
       dotenv (= 3.1.8)
       railties (>= 6.1)
     drb (2.2.3)
-    erb (2.2.3)
-      cgi
+    erb (5.0.1)
     erubi (1.13.1)
     execjs (2.10.0)
     faraday (2.12.2)