python-common: reformat ceph.deployment.service_spec import line

Quoting https://peps.python.org/pep-0008/#maximum-line-length
```
The preferred way of wrapping long lines is by using Python’s
implied line continuation inside parentheses, brackets and braces. Long
lines can be broken over multiple lines by wrapping expressions in
parentheses. These should be used in preference to using a backslash for
line continuation.
```

I also think it is much more readable and is similar to the style
applied by automated code formatting tools like `black`.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

src/python-common/ceph/deployment/drive_group.py

@@ -2,7 +2,11 @@ import enum
 import yaml
 
 from ceph.deployment.inventory import Device
-from ceph.deployment.service_spec import ServiceSpec, PlacementSpec, CustomConfig
+from ceph.deployment.service_spec import (
+    CustomConfig,
+    PlacementSpec,
+    ServiceSpec,
+)
 from ceph.deployment.hostspec import SpecValidationError
 
 try: