Fix typos in the dev guide regarding gf group size selection.

Change-Id: I038fc8cd4c85fad50018c9abee75ac8e7f3d671b
diff --git a/doc/dev_guide/tplgfgroupdiagram.png b/doc/dev_guide/tplgfgroupdiagram.png
index 582049a..fa5b067 100644
--- a/doc/dev_guide/tplgfgroupdiagram.png
+++ b/doc/dev_guide/tplgfgroupdiagram.png
Binary files differ