Doc: no midx and partial clone relation

The multi-pack index treats promisor packfiles (that is, packfiles that
have an accompanying .promisor file) the same as other packfiles. Remove
a section in the documentation that seems to indicate otherwise.

Signed-off-by: Jonathan Tan <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jonathantanmy

Documentation/technical/multi-pack-index.txt

@@ -89,11 +89,6 @@ Future Work
   helpful to organize packfiles by object type (commit, tree, blob,
   etc.) and use this metadata to help that maintenance.
 
-- The partial clone feature records special "promisor" packs that
-  may point to objects that are not stored locally, but available
-  on request to a server. The multi-pack-index does not currently
-  track these promisor packs.
-
 Related Links
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 [0] https://bugs.chromium.org/p/git/issues/detail?id=6