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/config.go b/android/config.go
index dcefdf3..567ebd8 100644
--- a/android/config.go
+++ b/android/config.go
@@ -2076,6 +2076,6 @@
 	return ret
 }
 
-func (c *config) BuildIgnoreApexContributionContents() *bool {
+func (c *config) BuildIgnoreApexContributionContents() []string {
 	return c.productVariables.BuildIgnoreApexContributionContents
 }