Update version of CMake for Jazzy to at least 3.20. (#393)

This is because we are using CMake 3.20 features in Jazzy
now.

Signed-off-by: Chris Lalancette <[email protected]>

rep-2000.rst

@@ -1127,7 +1127,7 @@ Dependency Requirements:
 +----------------+----------------+----------------+----------+---------------+------------------+---------------------+
 | Package        |  Ubuntu Noble  |  Windows 10**  |  RHEL 9  |    macOS**    | Debian Bookworm  |   OpenEmbedded**    |
 +================+================+================+==========+===============+==================+=====================+
-| CMake          |      3.27.7    |     3.22.0     |  3.20.2  |    3.14.4     |      3.25.1      | 3.22.3 / 3.16.5***  |
+| CMake          |      3.27.7    |     3.22.0     |  3.20.2  |    3.20.0     |      3.25.1      |       3.22.3        |
 +----------------+----------------+----------------+----------+---------------+------------------+---------------------+
 | EmPY           |      3.3.4     |     3.3.2      |   3.3.4  |                     3.3.4                              |
 +----------------+----------------+----------------+----------+---------------+------------------+---------------------+