[freeflow][test] Set larger timeout for sincos convergence test.
What this MR does / why does DuMux need it: test_ff_navierstokes_sincos currently has a timeout on buildbot. This MR gives the test more time.
Edited by Timo Koch
What this MR does / why does DuMux need it: test_ff_navierstokes_sincos currently has a timeout on buildbot. This MR gives the test more time.