Secrets: remove unused SecureValueMetadataStorage.ReadForDecrypt method (#108181)

* Secrets: remove unused SecureValueMetadataStorage.ReadForDecrypt method

* remove unused struct: secureValueForDecrypt

pkg/storage/secret/metadata/data/secure_value_read_for_decrypt.sql

@@ -1,13 +0,0 @@
-SELECT
-  {{ .Ident "keeper" }},
-  {{ .Ident "decrypters" }},
-  {{ .Ident "ref" }},
-  {{ .Ident "external_id" }},
-  {{ .Ident "active" }}
-FROM
-  {{ .Ident "secret_secure_value" }}
-WHERE 
-  {{ .Ident "namespace" }} = {{ .Arg .Namespace }} AND
-  {{ .Ident "name" }} = {{ .Arg .Name }} AND
-  {{ .Ident "active" }} = true
-;