kbuild: remove redundant FORCE definition in scripts/Makefile.modpost

The same code exists a few lines above.

Fixes: 436b2ac603d5 ("modpost: invoke modpost only when input files are updated")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 3651cbf..f54b6ac 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -124,9 +124,6 @@
 
 -include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 
-PHONY += FORCE
-FORCE:
-
 endif
 
 .PHONY: $(PHONY)