Remove implicit outputs for the flattened APEX Make module

When flattened, the Make module for an APEX is a phony package for the
files in it. There is no output (either implcit or explicit) there.

Bug: 144338929
Test: m
Test: check the generated Android-<target>.mk file
Change-Id: I86df3b69f402a7e2d94bafa39f2aad3312d8c28b

apex/androidmk.go

@@ -168,7 +168,6 @@ func (a *apexBundle) androidMkForType() android.AndroidMkData {
 					fmt.Fprintln(w, "LOCAL_REQUIRED_MODULES :=", strings.Join(moduleNames, " "))
 				}
 				fmt.Fprintln(w, "include $(BUILD_PHONY_PACKAGE)")
-				fmt.Fprintln(w, "$(LOCAL_INSTALLED_MODULE): .KATI_IMPLICIT_OUTPUTS :=", a.outputFile.String())
 
 			} else {
 				fmt.Fprintln(w, "\ninclude $(CLEAR_VARS)")