fix: upgrade session-store test assertions to patched AssertJ

Use3.27.7 for GHSA-rqfh-9r24-8c9r. Verified synthetic external-entity/DTD rejection, ordinary XML control, dependency resolution,67unit and29integration tests with coverage.

Co-Authored-By: Codex <noreply@openai.com>

pom.xml

@@ -137,7 +137,7 @@
       <dependency>
          <groupId>org.assertj</groupId>
          <artifactId>assertj-core</artifactId>
-         <version>3.27.3</version>
+         <version>3.27.7</version>
          <scope>test</scope>
       </dependency>