gdb: re-format with black 21.12b0

Run black 21.12b0 on gdb/, there is a single whitespace change.  I will
update the wiki [1] in parallel to bump the version of black to 21.12b0.

[1] https://sourceware.org/gdb/wiki/Internals%20GDB-Python-Coding-Standards

Change-Id: Ib3b859e3506c74a4f15d16f1e44ef402de3b98e2

gdb/python/lib/gdb/__init__.py

diff --git a/gdb/python/lib/gdb/__init__.py b/gdb/python/lib/gdb/__init__.py
index 7b6d870..1706337 100644
--- a/gdb/python/lib/gdb/__init__.py
+++ b/gdb/python/lib/gdb/__init__.py
@@ -243,7 +243,6 @@
         except:
             return None
 
-
 except:
 
     def colorize(filename, contents):