Update pyaaf2 requirement from ~=1.4.0 to >=1.4,<1.7 (#1355)

Updates the requirements on [pyaaf2](https://github.com/markreidvfx/pyaaf2) to permit the latest version.
- [Release notes](https://github.com/markreidvfx/pyaaf2/releases)
- [Commits](markreidvfx/pyaaf2@v1.4.0...v1.6.0)

---
updated-dependencies:
- dependency-name: pyaaf2
  dependency-type: direct:production
...

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setup.py

@@ -336,7 +336,7 @@ def test_otio():
     python_requires='>2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*, !=3.5.*, !=3.6.*, !=3.9.0',  # noqa: E501
 
     install_requires=[
-        'pyaaf2~=1.4.0',
+        'pyaaf2>=1.4,<1.7',
         'backports.tempfile; python_version<"3.0"',
         # Enables the builtins module in the XGES adapter
         'future; python_version<"3.0"',