Remove pip from pyproject.toml (#94)

In response to #91 (comment)

Co-authored-by: Sorin Sbarnea <[email protected]>

Author: grgmiller

pyproject.toml

@@ -1,6 +1,5 @@
 [build-system]
 requires = [
-  "pip >= 19.3.1",
   "setuptools >= 42",
   "setuptools_scm[toml] >= 3.5.0",
   "setuptools_scm_git_archive >= 1.1",