Fix #10821 Clear 'to do' in format specification history

Documents changes in `cabal-version: 1.14`.

(There were no changes in `cabal-version: 1.16`.)

Author: mpilgrem

doc/file-format-changelog.rst

@@ -287,13 +287,16 @@ relative to the respective preceding *published* version.
 
 * Add ``getSysconfDir`` operation to ``Paths_`` API.
 
-``cabal-version: 1.16``
+``cabal-version: 1.14``
 -----------------------
 
-.. todo::
+* New :pkg-section:`benchmark` stanza for describing a package benchmark added.
 
-   this needs to be researched; there were only few changes between
-   1.12 and 1.18;
+* ``exitcode-stdio-1.0`` is a valid value of the `type` field in a
+  :pkg-section:`benchmark` stanza.
+
+* ``detailed-0.9`` added as a valid value of the `type` field in a
+  :pkg-section:`test-suite` stanza.
 
 ``cabal-version: 1.12``
 -----------------------