revert(proposals): drop docs/proposals/batched-multi-kind-fetch.md

The design proposal does not belong in the SDK repo. Remove the file
and the .vale.ini exemption that existed only to keep vale silent on
the proposal's technical jargon.

Author: iddocohen

.vale.ini

@@ -30,11 +30,3 @@ BasedOnStyles = Infrahub
 BasedOnStyles = Infrahub, GeneratedRef
 Infrahub.spelling = NO
 BlockIgnores = (?s) *((import.*?\n)|(```.*?```\n))
-
-# Design proposals are author-facing engineering documents, not published
-# Docusaurus content. They live in docs/proposals/ rather than docs/docs/
-# and contain technical jargon (subselection, dedup, Dataloader,
-# SQLAlchemy, etc.) that would pollute the Infrahub spelling dictionary
-# if added globally.
-[docs/proposals/**/*.md]
-BasedOnStyles =