[tests] remove directory 'reject'

src/plugins/e-acsl/Makefile.in

src/plugins/e-acsl/tests/reject/function_declaration.i

...-acsl/tests/reject/oracle/function_declaration.err.oracle

...-acsl/tests/reject/oracle/function_declaration.res.oracle

src/plugins/e-acsl/tests/reject/oracle/quantif.res.oracle

src/plugins/e-acsl/tests/reject/quantif.i

src/plugins/e-acsl/tests/reject/result/.gitkeep

src/plugins/e-acsl/tests/reject/test_config