doc: fix warning with meson

doc: fix warning with meson

The install parameter to configure_file is new in 0.50 and generates a
warning since it is newer than our minimum version of 0.47.1. The
parameter, however, is unneeded as the documentation states:

"When omitted it defaults to true when install_dir is set and not empty,
false otherwise."

Given that install_dir is not set for this file, install defaults to false
so no need to explicitly specify it.

Fixes: 720b14db3ae2 ("build: generate API documentation with meson")
Cc: stable@dpdk.org
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Acked-by: Luca Boccassi <bluca@debian.org>