Remove legacy javax.mail dependency from test-utils-core

Part of Jakarta EE 10 migration — javax.mail replaced by
jakarta.mail-api throughout the platform.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: allanmckenzie

framework-utilities/test-utils/test-utils-core/pom.xml

@@ -17,10 +17,6 @@
             <groupId>org.glassfish</groupId>
             <artifactId>jakarta.json</artifactId>
         </dependency>
-        <dependency>
-            <groupId>com.sun.mail</groupId>
-            <artifactId>javax.mail</artifactId>
-        </dependency>
         <dependency>
             <groupId>org.jboss.resteasy</groupId>
             <artifactId>resteasy-client</artifactId>