Schema header translates to Configuration Reference (#2350)

When transforming installation docs, the "Schema" header should
transform the same way as "Argument Regerence". This PR adds that
behavior.

pkg/tfgen/installation_docs.go

@@ -135,6 +135,9 @@ func applyEditRules(contentBytes []byte, docFile string, g *Generator) ([]byte,
 			`The following configuration inputs are supported`),
 		reReplace(`Argument Reference`,
 			`Configuration Reference`),
+		reReplace(`Schema`,
+			`Configuration Reference`),
+		reReplace("### Optional\n", ""),
 		reReplace(`block contains the following arguments`,
 			`input has the following nested fields`),
 	)