Replace abandoned fakeredis with real redis, upgrade redis-rb to 5.x (#22)

fakeredis is unmaintained (last release 0.9.2, 2023) and hard-pins
redis ~> 4.8, which kept redis-rb stuck at 4.8.1 across every Dependabot
bump. Drop it in favor of testing against a real redis server.

- Remove fakeredis from the Gemfile and the spec/support stub
- Relock: redis 4.8.1 -> 5.4.1 (pulls in redis-client)
- Add a redis service to the CI test_and_lint job, since fakeredis was
  previously the only reason specs passed without a server

Specs need no changes: redis-rb 5 connects lazily, so type assertions
and verify!/quit work against the live server.

Author: dduugg

.github/workflows/ci.yml

@@ -17,6 +17,16 @@ jobs:
     env:
       BUNDLE_GEMFILE: Gemfile
     name: "Test and lint: Ruby ${{ matrix.ruby }}"
+    services:
+      redis:
+        image: redis
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
     steps:
       - uses: actions/checkout@v4
       - name: Set up Ruby ${{ matrix.ruby }}

Gemfile

@@ -8,5 +8,4 @@ gemspec
 gem "rake"
 gem "rspec"
 gem "standard"
-gem "fakeredis"
 gem "connection_pool"

Gemfile.lock

@@ -48,8 +48,6 @@ GEM
     diff-lcs (1.6.2)
     drb (2.2.3)
     erubi (1.12.0)
-    fakeredis (0.9.2)
-      redis (~> 4.8)
     i18n (1.15.2)
       concurrent-ruby (~> 1.0)
     io-console (0.7.2)
@@ -116,7 +114,10 @@ GEM
     rake (13.4.2)
     rdoc (6.6.3.1)
       psych (>= 4.0.0)
-    redis (4.8.1)
+    redis (5.4.1)
+      redis-client (>= 0.22.0)
+    redis-client (0.30.0)
+      connection_pool
     regexp_parser (2.12.0)
     reline (0.5.7)
       io-console (~> 0.5)
@@ -189,7 +190,6 @@ PLATFORMS
 DEPENDENCIES
   bigrails-redis!
   connection_pool
-  fakeredis
   rake
   rspec
   standard