git: remove obsolete todo item

The changes in 02c47b74366c cleaned up the requirement check.

hgext/git/TODO.md

@@ -1,39 +1,30
 Octopus Merge Support
 =====================
 
 This will be moderately complicated, as we'll need to synthesize phony
 changeset entries to explode the octopus into "revisions" that only
 have two parents each. For today, we can probably just do something like
 
     aaaaaaaaaaaaaaaaaaXX{20 bytes of exploded node's hex sha}
 
 where XX is a counter (so we could have as many as 255 parents in a
 git commit - more than I think we'd ever see.) That means that we can
 install some check in this extension to disallow checking out or
 otherwise interacting with the `aaaaaaaaaaaaaaaaaa` revisions.
 
 
 Interface Creation
 ====================
 
 We at least need an interface definition for `changelog` in core that
 this extension can satisfy, and again for `basicstore`.
 
 
 Reason About Locking
 ====================
 
 We should spend some time thinking hard about locking, especially on
 .git/index etc. We're probably adequately locking the _git_
 repository, but may not have enough locking correctness in places
 where hg does locking that git isn't aware of (notably the working
 copy, which I believe Git does not lock.)
-
-Clean up requirements
-=====================
-
-Right now (for historical reasons, mainly) hgext.git uses a
-.hg/this-is-git file to detect repositories that should be treated as
-git. We should look in the .hg/requires for the "git" requirement
-instead (we already set this requirement, so it's mostly keying off
-that instead of using an empty file.)