Minor fix to Python breakpoint event documentation

I noticed that the Python event documentation referred to the event's
"breakpoint" field as a function, whereas it is actually an attribute.
This patch fixes the error.

gdb/doc/python.texi

diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index ba5a9b3..aaf7666 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -3448,9 +3448,9 @@
 @end defvar
 
 @defvar BreakpointEvent.breakpoint
-A reference to the first breakpoint that was hit.
-This function is maintained for backward compatibility and is now deprecated 
-in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
+A reference to the first breakpoint that was hit.  This attribute is
+maintained for backward compatibility and is now deprecated in favor
+of the @code{gdb.BreakpointEvent.breakpoints} attribute.
 @end defvar
 
 @item events.new_objfile