Typo fix unncessary -> unnecessary.

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

doc/devblog/day_378__finishing_adjusted_branches_merge.mdwn

@@ -1,6 +1,6 @@
 Well, I had to rethink how merges into adjusted branches should be handled.
 The old method often led to unnecessary merge conflicts. My new approach
-should always avoid unncessary merge conflicts, but it's quite a trick.
+should always avoid unnecessary merge conflicts, but it's quite a trick.
 
 To merge origin/master into adjusted/master, it first merges origin/master
 into master. But, since adjusted/master is checked out, it has to do the

doc/devblog/day_483__faster_start_with_removable_drives.mdwn

@@ -3,7 +3,7 @@ repository it's running in. That's been optimised some before, but
 not entirely eliminated; it's just too useful to have that information
 always available inside git-annex. But it turned out that it was doing more work
 than needed for many commands, by checking the git config of local remotes.
-Thas caused unncessary spin up of removable drives, or automount timeouts,
+Thas caused unnecessary spin up of removable drives, or automount timeouts,
 or generally more work than needed when running commands like `git annex
 find` and even tab completing git-annex. That's fixed now, so it
 avoids checking the git config of remotes except when running commands that

doc/devblog/day_487__git-annex-shell_p2pstdio.mdwn

@@ -4,7 +4,7 @@ this.
 
 The only complication was that git-annex-shell has a readonly mode,
 so the protocol server needed modifications to support that.
-Well, there's also some innefficiency around unncessary verification
+Well, there's also some innefficiency around unnecessary verification
 of transferred content in some cases, which will probably need extensions
 to the P2P protocol later.
 

doc/devblog/day_570__brrr.mdwn

@@ -11,7 +11,7 @@ I got sidetracked with how S3 prepares a handle to the server. That didn't
 work as well as it might have; most of the time each request to the remote
 actually prepared a new handle, rather than reusing a single handle. Though
 the http connection to the server did get reused, that still caused a lot
-of unncessary work. I fixed that, and the fix also allowed me to
+of unnecessary work. I fixed that, and the fix also allowed me to
 restructure export actions in the way I need for progress bars.
 
 I've ran out of time to finish adding the missing progress bars today, so