Update python-dotenv requirement from <0.19,>=0.17 to >=0.17,<0.20

Updates the requirements on [python-dotenv](https://github.com/theskumar/python-dotenv) to permit the latest version.
- [Release notes](https://github.com/theskumar/python-dotenv/releases)
- [Changelog](https://github.com/theskumar/python-dotenv/blob/master/CHANGELOG.md)
- [Commits](theskumar/python-dotenv@v0.17.0...v0.19.0)

---
updated-dependencies:
- dependency-name: python-dotenv
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements/base.txt

@@ -2,6 +2,6 @@
 # --------------------
 click>=8,<9
 click-log>=0.3,<0.4
-python-dotenv>=0.17,<0.19
+python-dotenv>=0.17,<0.20
 semver>=2,<3
 send2trash>=1.7,<1.18

setup.py

@@ -20,7 +20,7 @@
     install_requires=[
         "click>=7.1,<9",
         "click-log>=0.3,<0.4",
-        "python-dotenv>=0.17,<0.19",
+        "python-dotenv>=0.17,<0.20",
         "send2trash==1.6.0b1",
     ],
     entry_points="""