Correct APPLIBS reference

[lbt]

Explain how to use APPLIBSV1 and APPLIBSV2

Problem

The docs about APPLIBS are wrong.

Solution

Fix the docs!

Steps to Test

These variables are already tested in build/test/libs.bat

References

https://community.particle.io/t/using-applibs-with-local-toolchain/35837/7

---

Completeness

• [x] User is totes amazing for contributing!
• [x] Contributor has signed CLA (Info here)
• [x] Problem and Solution clearly stated
• [ ] Run unit/integration/application tests on device
• [x] Added documentation
• [ ] Added to CHANGELOG.md after merging (add links to docs and issues)

[lbt]

ping

[emdash]

LGTM