Drop older SWUpdate 2021.04

Signed-off-by: Stefano Babic <sbabic@denx.de>

recipes-support/swupdate/swupdate_2021.04.bb

@@ -1,5 +0,0 @@
-require swupdate.inc
-
-SRCREV = "47a1246435fdb78fba15cc969596994130412956"
-
-LIC_FILES_CHKSUM += "file://LICENSES/BSD-2-Clause.txt;md5=6a31f076f5773aabd8ff86191ad6fdd5"