fix OP_PLUGIN_ALIASES_SOURCED env variable

[jbhannah]

Overview

update environment variable name to indicate plugin aliases have been sourced.

Type of change

• [ ] Created a new plugin
• [ ] Improved an existing plugin
• [ ] Fixed a bug in an existing plugin
• [x] Improved contributor utilities or experience

Related Issue(s)

• Relates: #378, possibly resolves?

How To Test

Changelog

• renamed instances of OP_PLUGINS_SOURCED to OP_PLUGIN_ALIASES_SOURCED to match ~/.config/op/plugins.sh.