Fix error about having a mutable default for field headers in dataclass

Newer versions of Python error out on mutable default fields in a
dataclass, and the fix for that appears to be using the
`default_factory` attribute in `field`. This appears to at least pass
the tests.

Signed-off-by: Saikrishna Arcot <[email protected]>

Author: saiarcot895

sonic_package_manager/constraint.py

@@ -117,7 +117,7 @@ class PackageConstraint:
 
     name: str
     constraint: VersionConstraint
-    _components: ComponentConstraints = ComponentConstraints({})
+    _components: ComponentConstraints = field(default_factory=ComponentConstraints)
 
     def __str__(self): return f'{self.name}{self.constraint}'