Typo fix unncessary -> unnecessary.

Detected while reading recent CHANGELOG entry but then decided to apply
to entire codebase and docs since why not?

Remote/Borg.hs

@@ -223,7 +223,7 @@ listImportableContentsM u borgrepo c = prompt $ do
 			    (reqsz, retsz) = case extra of
 				" link to " -> (Nothing, fromMaybe sz . fromKey keySize)
 				_ -> (Just sz, const sz)
-			-- This does a little unncessary work to parse the 
+			-- This does a little unnecessary work to parse the 
 			-- key, which is then thrown away. But, it lets the
 			-- file list be shrank down to only the ones that are
 			-- importable keys, so avoids needing to buffer all

Remote/GCrypt.hs

@@ -355,7 +355,7 @@ shellOrRsync r ashell arsync
  -
  - (For shared encryption, gcrypt's default behavior is used.)
  -
- - Also, sets gcrypt-publish-participants to avoid unncessary gpg
+ - Also, sets gcrypt-publish-participants to avoid unnecessary gpg
  - passphrase prompts.
  -}
 setGcryptEncryption :: ParsedRemoteConfig -> String -> Annex ()

Remote/Helper/ExportImport.hs

@@ -143,7 +143,7 @@ adjustExportImport' isexport isimport r rs = do
 			else importUnsupported
 		, storeKey = \k af p ->
 			-- Storing a key on an export could be implemented,
-			-- but it would perform unncessary work
+			-- but it would perform unnecessary work
 			-- when another repository has already stored the
 			-- key, and the local repository does not know
 			-- about it. To avoid unnecessary costs, don't do it.