impress tables are not interactively growing

the optimization here stops tables growing as their text
contents change in editing mode

So, just recalculate if the table could grow and its
being interactively edited, which leaves the original
(dubious ?) load-time optimization in place

Change-Id: I894acf47d34ec8b68aaf9076b5a0cb7e29c38a17
(cherry picked from commit 22ef69b25fa60f4543dc72cb7a8d2f88b789ce43)
Signed-off-by: Stephan Bergmann <sbergman@redhat.com>