meta-ieisystems: fp5280g3: bmcweb: remove bbappend

This file is no longer needed.
openbmc/openbmc@7fabe70
added it.

https://gerrit.openbmc.org/c/openbmc/bmcweb/+/69228 enabled
redfish-new-powersubsystem-thermalsubsystem by default remove it here in
the bbappend to keep things cleaner. Since this is the only one in the
bbappend, just remove the whole file.

Tested: I tested having this line removed in the meta-ibm bbappend when
testing 69228.

Change-Id: I12e8ee2b4e89529f56227c26eb2be809d38b7de2
Signed-off-by: Gunnar Mills <[email protected]>