Adds "LSP" to spelling exceptions list

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What does this MR do?

Adds LSP (Language Server Protocol) to spelling list. Not so common a phrase in the gitlab repo, but it's constant in the groupeditor extensions repos. I've added it downstream to calm down the spelling-results noise, but if I don't add it here as well, it'll get overwritten in the next tooling update.

(https://microsoft.github.io/language-server-protocol/)

Related issues

Related to Open File Tabs User Facing Documentation - Adva... (gitlab-org/editor-extensions/gitlab-lsp#256 - closed) which is why I'm editing that file today

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