* docs: some final 2.6.0 updates

* docs: better warning text

* fix: Intel 18+ fully supported

* fix: Intel compiler workaround no longer needed

Followup on #94 now that Intel 18+ is required.

* Update PGI to 20.9

Update PGI to 20.9

* Update ci.yml

* Update ci.yml

* Update README.rst

* Update ci.yml

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

* Remove code inside 'PYPY_VERSION_NUM < 0x06000000' preprocessor if branch

* fix: more cleanup

* Remove more references to PyPy 5.7 and 5.9 in the docs

* Update comment on PyUnicode_UTF* in PyPy

Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>

* ci: fix broken documenation test (works on RtD)

* docs: docs link incorrect