Revert "Convert BuildIgnoreApexContritbutions variable to a boolean"

This revert was created by Android Culprit Assistant. The culprit was identified in the following culprit search session (http://go/aca-get/53721efb-c49e-4ce8-b96c-fd03598b4202).

Change-Id: I197b03b650bc6c22ff3c5eb9605522fd9650e98f
diff --git a/android/variable.go b/android/variable.go
index 7a49a68..73f5bfd 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -495,7 +495,7 @@
 
 	BuildFromSourceStub *bool `json:",omitempty"`
 
-	BuildIgnoreApexContributionContents *bool `json:",omitempty"`
+	BuildIgnoreApexContributionContents []string `json:",omitempty"`
 
 	HiddenapiExportableStubs *bool `json:",omitempty"`