base: remove redundant allowed content type for Solver Type

This is already defined in erp5_simulation, also Solver Type does not
exist in erp5_base

bt5/erp5_base/bt/template_portal_type_allowed_content_type_list

@@ -87,5 +87,4 @@ Person | Fax
 Person | Link
 Person | Telephone
 Query Module | Query
-Rounding Tool | Rounding Model
-Solver Tool | Solver Type
+Rounding Tool | Rounding Model
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