Magic numbers should be moved to constants.h

[reinhold-willcox]

Describe the bug
There are some magic numbers in the *WD.cpp/h files which should be named and moved into constants.h.

This issue is extremely minor / low priority, but probably good for a first issue for any newcomers.

Label the issue
urgency_low - This issue is not urgent
severity_minor - This is a minor bug with minimal impact

To Reproduce
I see some in HeWD::DetermineAccretionRegime

Versioning (please complete the following information):

• COMPAS v03.15.01

Additional context
Add any other context about the problem here.

[ilyamandel]

Addressed in #1386, closing.