fix deprecation warnings
Fixes a warning:
../../../cvmfs/lhcbdev.cern.ch/nightlies/lhcb-run2-patches/latest/Phys_v27r3/InstallArea/x86_64_v2-centos7-gcc11-opt/python/LoKiPhys/Phys.py:597
/cvmfs/lhcbdev.cern.ch/nightlies/lhcb-run2-patches/latest/Phys_v27r3/InstallArea/x86_64_v2-centos7-gcc11-opt/python/LoKiPhys/Phys.py:597: DeprecationWarning: invalid escape sequence \s
"""Get the transverse mass (with uncertainty) of the particle
../../../cvmfs/lhcbdev.cern.ch/nightlies/lhcb-run2-patches/latest/Phys_v27r3/InstallArea/x86_64_v2-centos7-gcc11-opt/python/LoKiPhys/Phys.py:614
/cvmfs/lhcbdev.cern.ch/nightlies/lhcb-run2-patches/latest/Phys_v27r3/InstallArea/x86_64_v2-centos7-gcc11-opt/python/LoKiPhys/Phys.py:614: DeprecationWarning: invalid escape sequence \s
"""Get the transverse kinetic energy (with uncertainty) of the particle
-- Docs: https://docs.pytest.org/en/stable/warnings.html