feature/plymouth: Fix syntax error

During refactoring, the end of the line was removed.

Fixes: a8b613f ("features: Run shell code only once")
Signed-off-by: Alexey Gladkov <[email protected]>

Author: legionus

features/plymouth/rules.mk

@@ -2,7 +2,7 @@
 PLYMOUTH_DIRS := $(foreach d,$(LIB_DIRS),$(wildcard $(d)/plymouth))
 
 $(call assign-shell-once,PLYMOUTH_PACK_MODULES, $(FEATURESDIR)/plymouth/bin/get-modules)
-$(call assign-shell-once,PLYMOUTH_PACK_THEME,   $(FEATURESDIR)/plymouth/bin/get-theme-files "$(PLYMOUTH_THEME)
+$(call assign-shell-once,PLYMOUTH_PACK_THEME,   $(FEATURESDIR)/plymouth/bin/get-theme-files "$(PLYMOUTH_THEME)")
 $(call assign-shell-once,PLYMOUTH_PACK_DEFFONT, fc-match -f '%{file}\n' 'DejaVuSans' ||:)
 
 PLYMOUTH_PACK_FONT := $(or $(PLYMOUTH_FONT),$(PLYMOUTH_PACK_DEFFONT))