Added macOS path instructions (issue #410)

[ekansa]

brief description of changes

Updates macOS dependency path related instructions.

issues addressed

https://github.com/archesproject/arches-docs/issues/409 https://github.com/archesproject/arches-docs/issues/410

further comments

See changes previewed here: https://arches.readthedocs.io/en/mac_7_5/installing/requirements-and-dependencies/

and

https://arches.readthedocs.io/en/mac_7_5/installing/installation/

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This box must be checked

• [x] the PR branch was originally made from the base branch

This box should be checked

• [x] after these changes the docs build locally without error

This box should only be checked you intend to follow through on it (we can do it on our end too)

• [x] I will cherry-pick all commits in this PR into other branches that should have them after this PR is merged

[whatisgalen]

@ekansa for my suggested changes, would it be more convenient for me to write them here or to just commit to your branch?

[ekansa]

@ekansa for my suggested changes, would it be more convenient for me to write them here or to just commit to your branch?

You're welcome to commit directly to the branch! Thanks!

[ekansa]

@whatisgalen @jacobtylerwalls Are we OK to merge this PR?