meta-ibm: remove nginx from IBM platforms.

Nginx on OpenBMC has a number of issues that matter to openbmc.

1. It increases the binary size.  This is an issue given that OpenBMC
targets a relatively minimal flash footprint.
2. It increases the runtime overhead.  Running nginx as a reverse proxy
to the application servers causes a runtime overhead, and context switch
for every single page load, as well as an extra socket.
3. nginx doesn't implement any kind of authentication, so auth needs to
be implemented in every application server.  This removes a lot of the
advantages of the reverse proxy, and duplicates a lot of code amongst
multiple application servers
4. A number of nginx parameters run from the nginx config file.  Some of
these parameters (like cipher suite support) are desired to be changed
at runtime, rather than fixed at compile time.

Related to commit here to move system to bmcweb:
https://gerrit.openbmc-project.xyz/#/c/openbmc/meta-phosphor/+/12933/

Change-Id: I988fce8dae565808bd0eeacd8b7a71f3cc06d98f
Signed-off-by: Ed Tanous <ed.tanous@intel.com>
(cherry picked from commit 699e296)

recipes-phosphor/packagegroups/packagegroup-obmc-apps.bbappend

@@ -1,2 +1,3 @@
 RDEPENDS_${PN}-logging += "ibm-logging"
-RDEPENDS_${PN}-extras += "nginx bmcweb"
+RDEPENDS_${PN}-extras += " bmcweb"
+RDEPENDS_${PN}-remove += " phosphor-rest phosphor-gevent"