remove trivial goals from sessions

...erifythis_2018_array_based_queuing_lock_1/why3session.xml

.../verifythis_2018_array_based_queuing_lock_1/why3shapes.gz

...erifythis_2018_array_based_queuing_lock_2/why3session.xml

.../verifythis_2018_array_based_queuing_lock_2/why3shapes.gz

examples/verifythis_2018_mind_the_gap_1/why3session.xml

examples/verifythis_2018_mind_the_gap_1/why3shapes.gz

examples/verifythis_2018_mind_the_gap_2/why3session.xml

examples/verifythis_2018_mind_the_gap_2/why3shapes.gz

examples/verifythis_fm2012_treedel/why3session.xml

examples/verifythis_fm2012_treedel/why3shapes.gz

examples/vstte12_combinators/why3session.xml

examples/vstte12_combinators/why3shapes.gz

examples/vstte12_tree_reconstruction/why3session.xml

examples/vstte12_tree_reconstruction/why3shapes.gz