Move #12403, #12513 users guide notes to 8.2.1 release notes

The changes in #12403 and #12513 subtly changed the behavior of Template
Haskell reification and splicing. While the old behavior was certainly buggy,
it's possible that there's code in the wild that depended on the old behavior
to work. To err on the side of caution, I'll postpone these changes to GHC
8.2.1 instead of having them merged into GHC 8.0.2.

docs/users_guide/8.0.2-notes.rst

@@ -32,17 +32,6 @@ Compiler
    initial cmm from STG-to-C-- code generation and :ghc-flag:`-ddump-cmm-verbose`
    to obtain the intermediates from all C-- pipeline stages.
 
-Template Haskell
-~~~~~~~~~~~~~~~~
-
--  Reifying types that contain unboxed tuples now works correctly. (Previously,
-   Template Haskell reified unboxed tuples as boxed tuples with twice their
-   appropriate arity.)
-
--  Splicing singleton unboxed tuple types (e.g., ``(# Int #)``) now works
-   correctly. Previously, Template Haskell would implicitly remove the
-   parentheses when splicing, which would turn ``(# Int #)`` into ``Int``.
-
 TODO FIXME Heading title
 ~~~~~~~~~~~~~~~~~~~~~~~~
 

docs/users_guide/8.2.1-notes.rst

@@ -56,6 +56,14 @@ Template Haskell
 
       f x = $(addModFinalizer (reify 'x >>= runIO . print) >> [| x |])
 
+-  Reifying types that contain unboxed tuples now works correctly. (Previously,
+   Template Haskell reified unboxed tuples as boxed tuples with twice their
+   appropriate arity.)
+
+-  Splicing singleton unboxed tuple types (e.g., ``(# Int #)``) now works
+   correctly. Previously, Template Haskell would implicitly remove the
+   parentheses when splicing, which would turn ``(# Int #)`` into ``Int``.
+
 Runtime system
 ~~~~~~~~~~~~~~