Update dependency python-dotenv to v0.21.1 (#150)

Author: renovate[bot]

requirements.txt

@@ -6,7 +6,7 @@ loguru==0.6.0; python_version >= "3.5"
 paramiko==2.11.0
 pycparser==2.21; python_version >= "3.6" and python_full_version < "3.0.0" or python_full_version >= "3.4.0" and python_version >= "3.6"
 pynacl==1.5.0; python_version >= "3.6"
-python-dotenv==0.20.0; python_version >= "3.5"
+python-dotenv==0.21.1; python_version >= "3.5"
 scp==0.14.4
 six==1.16.0; python_version >= "2.7" and python_full_version < "3.0.0" or python_full_version >= "3.3.0"
 win32-setctime==1.1.0; sys_platform == "win32" and python_version >= "3.5"