CI against bundler 2.5.15

Author: ccutrer

.github/workflows/ci.yml

@@ -14,12 +14,12 @@ jobs:
       fail-fast: false
       matrix:
         ruby-version: [2.6, 2.7, "3.0", 3.1, 3.2, 3.3]
-        bundler-version: [2.4.19, 2.4.22, 2.5.10]
+        bundler-version: [2.4.19, 2.4.22, 2.5.15]
         exclude:
           - ruby-version: 2.6
-            bundler-version: 2.5.10
+            bundler-version: 2.5.15
           - ruby-version: 2.7
-            bundler-version: 2.5.10
+            bundler-version: 2.5.15
     env:
       BUNDLER_VERSION: ${{ matrix.bundler-version }}
       BUNDLE_LOCKFILE: active