Draft: Remove un-necessary monkey-patching of attr_encrypted
This patch was added in gitlab-foss!667 (merged), and since fixed upstream in https://github.com/attr-encrypted/attr_encrypted/pull/160.
The implementation of attribute_instance_methods_as_symbols was later changed to use connected? method instead but this achieved the same goal of not connecting to the database when there's none defined.
Furthermore, we now effectively stop using attribute_instance_methods_as_symbols, by patching out attribute_instance_methods_as_symbols_available?
Also adds a raise if we attempt to upgrade attr_encrypted past 3.1.0.
Edited by Thong Kuah