doc: git-pull: delete the example

From user feedback: this example is confusing because it implies that
`git pull` will run `git merge` by default, but the default is
`--ff-only`.

We could instead show an example of a fast-forward merge, but that may
not add a lot since fast-forward merges are relatively simple. This lets
us keep the description short.

Signed-off-by: Julia Evans <[email protected]>

Author: jvns

Documentation/git-pull.adoc

@@ -30,32 +30,6 @@ branch. There are 4 main options for integrating the remote branch:
 You can also set the configuration options `pull.rebase`, `pull.squash`,
 or `pull.ff` with your preferred behaviour.
 
-Assume the following history exists and the current branch is
-"`master`":
-
-------------
-	  A---B---C master on origin
-	 /
-    D---E---F---G master
-	^
-	origin/master in your repository
-------------
-
-Then "`git pull`" will fetch and replay the changes from the remote
-`master` branch since it diverged from the local `master` (i.e., `E`)
-until its current commit (`C`) on top of `master` and record the
-result in a new commit along with the names of the two parent commits
-and a log message from the user describing the changes.
-
-------------
-	  A---B---C origin/master
-	 /         \
-    D---E---F---G---H master
-------------
-
-See linkgit:git-merge[1] for details, including how conflicts
-are presented and handled.
-
 In Git 1.7.0 or later, to cancel a conflicting merge, use
 `git reset --merge`.  *Warning*: In older versions of Git, running 'git pull'
 with uncommitted changes is discouraged: while possible, it leaves you