gdb/python: reformat file with black

Reformat a Python file with black after this commit:

  commit 59912fb2d22f8a4bb0862487f12a5cc65b6a013f
  Date:   Tue Sep 19 11:45:36 2023 +0100

      gdb: add Python events for program space addition and removal

There should be no functional change with this commit.

gdb/testsuite/gdb.python/py-progspace-events.py

@@ -19,11 +19,14 @@
 import gdb
 import gdb.events
 
+
 def new_progspace(event):
     print("NewProgspaceEvent: %s" % str(event.progspace))
 
+
 def free_progspace(event):
     print("FreeProgspaceEvent: %s" % str(event.progspace))
 
+
 gdb.events.new_progspace.connect(new_progspace)
 gdb.events.free_progspace.connect(free_progspace)