User-Agent field-value doesn't follow format conventions

[Daviey]

Minor issue with the User-Agent field value not following the convention of rfc7231 or rfc2616.

python-htb/htb/connection.py

Line 125 in 940d11d

"User-Agent": "https://github.com/calebstewart/python-htb",

python-htb/htb/connection.py

Line 163 in 940d11d

headers = {"User-Agent": "https://github.com/calebstewart/python-htb"}