patchtest: Fix minor README typo

Fix minor typo in patchtest.README.

(From OE-Core rev: a0531c99b9aa328f28904ffdad8883d5e739436a)

Signed-off-by: Sofiane HAMAM <sofiane.hamam@smile.fr>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/patchtest.README

@@ -69,7 +69,7 @@ the target project, but these parameters can be configured using the `--limit`,
 To run patchtest on the host, do the following:
 
 1. In openembedded-core/poky, do `source oe-init-build-env`
-2. Generate patch files from the target repository by doing `git-format patch -N`,
+2. Generate patch files from the target repository by doing `git format-patch -N`,
    where N is the number of patches starting at HEAD, or by using git-pw
    or patchtest-get-series
 3. Run patchtest on a patch file by doing the following: