Use SegmentInjectorModifier in the PatchMaker user-guide.md

Simplify the docs to use the SegmentInjectorModifier instead of manually injecting with the BinaryPatchModifier.

[x] I have reviewed the OFRAK contributor guide and attest that this pull request is in accordance with it.

One sentence summary of this PR (This should go in the CHANGELOG!) Simplify the PatchMaker docs

Please describe the changes in your request. Simplify the PatchMaker docs

Anyone you think should look at this, specifically?

redballoonsecurity / ofrak