build: upgrade to rebar3 version 3.14.3-emqx-8

relup could not read appup file error reason was not printed
rebar3 3.24.3-8 (with relx 4.3.0-emqx-3) fixed it

Makefile

@@ -1,5 +1,5 @@
 $(shell $(CURDIR)/scripts/git-hooks-init.sh)
-REBAR_VERSION = 3.14.3-emqx-7
+REBAR_VERSION = 3.14.3-emqx-8
 REBAR = $(CURDIR)/rebar3
 BUILD = $(CURDIR)/build
 SCRIPTS = $(CURDIR)/scripts