bpo-30769: Fix reference leak introduced in 77703942c59 (#2416)

New error condition paths were introduced, which did not decrement
`key2` and `val2` objects.  Therefore, decrement references before
jumping to the error label.

Signed-off-by: Eric N. Vander Weele <ericvw@gmail.com>
diff --git a/Misc/ACKS b/Misc/ACKS
index 89cd1fa..a6d1e0f 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1611,6 +1611,7 @@
 Case Van Horsen
 John Mark Vandenberg
 Kyle VanderBeek
+Eric N. Vander Weele
 Andrew Vant
 Atul Varma
 Dmitry Vasiliev