[test] Remove 1ptracer test -> replaced by 1ptracer example

test/porousmediumflow/tracer/1ptracer/CMakeLists.txt

test/porousmediumflow/tracer/1ptracer/main.cc

test/porousmediumflow/tracer/1ptracer/params.input

test/porousmediumflow/tracer/1ptracer/problem_1p.hh

test/porousmediumflow/tracer/1ptracer/problem_tracer.hh

test/porousmediumflow/tracer/1ptracer/spatialparams_1p.hh

.../porousmediumflow/tracer/1ptracer/spatialparams_tracer.hh

test/porousmediumflow/tracer/CMakeLists.txt