remove work repetitions for 'the'

doc/src/Section_howto.txt

doc/src/compute_chunk_atom.txt

doc/src/dihedral_table.txt

doc/src/dump_modify.txt

doc/src/fix_deform.txt

doc/src/fix_langevin.txt

doc/src/fix_rx.txt

doc/src/fix_smd_adjust_dt.txt

doc/src/fix_srd.txt

doc/src/fix_ttm.txt

doc/src/improper_style.txt

doc/src/neb.txt

doc/src/next.txt

doc/src/pair_srp.txt

doc/src/prd.txt

doc/src/python.txt

doc/src/read_dump.txt

doc/src/tad.txt

doc/src/tutorial_drude.txt