Fix[mqbnet]: Remove extra alloc argument from UT

`bsl::allocate_shared` automatically forwards the allocator to the
constructor of the object it is building correctly.  Passing the
allocator in addition causes a compiler error.  This patch removes the
extra allocator from a UT.

Signed-off-by: Patrick M. Niedzielski <pniedzielski@bloomberg.net>

Author: pniedzielski

src/groups/mqb/mqbnet/mqbnet_initialconnectioncontext.t.cpp

@@ -175,8 +175,7 @@ static void test1_initialConnectionContext()
                     "testMechanism",
                     authnMsg,
                     bmqp::EncodingType::e_BER,
-                    mqbnet::AuthenticationState::e_AUTHENTICATING,
-                    alloc);
+                    mqbnet::AuthenticationState::e_AUTHENTICATING);
             obj.setAuthenticationContext(authnCtx);
             BMQTST_ASSERT_EQ(authnCtx, obj.authenticationContext());
         }