Remove mentions of "long integer" in the docs.

Credits to HappySmileMan from GHOP.
diff --git a/Doc/library/pickle.rst b/Doc/library/pickle.rst
index e186937..c88fc29 100644
--- a/Doc/library/pickle.rst
+++ b/Doc/library/pickle.rst
@@ -328,7 +328,7 @@
 
 * ``None``, ``True``, and ``False``
 
-* integers, long integers, floating point numbers, complex numbers
+* integers, floating point numbers, complex numbers
 
 * normal and Unicode strings