refactor(HttpFirewallConfigTest): use expression lambda

solidify-authorization-server/src/test/java/ch/unige/solidify/auth/HttpFirewallConfigTest.java

@@ -93,9 +93,7 @@ class HttpFirewallConfigTest {
   private void testInvalidHeader(HttpFirewall httpFirewall, String headerValue) {
     MockHttpServletRequest request = this.getRequest(headerValue);
     FirewalledRequest firewalledRequest = httpFirewall.getFirewalledRequest(request);
-    assertThrows(RequestRejectedException.class, () -> {
-      firewalledRequest.getHeader(HEADER_NAME);
-    });
+    assertThrows(RequestRejectedException.class, () -> firewalledRequest.getHeader(HEADER_NAME));
   }
 
   private MockHttpServletRequest getRequest(String headerValue) {