Fix referenced images in README-1.6.7

Before, only one image was referenced, consisting of a screenshot of two
diagrams. The other image file, containing just one of the diagrams, was
not used. Now, both images have been cropped correctly and are both
referenced separately from the release notes.

Better late than never...

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

docs/release/README-1.6.7.adoc

@@ -94,7 +94,9 @@ when load time weaving a small application loading in Tomcat. For each
 of 10 iterations (x axis), the top comparison is startup time in
 milliseconds, the lower comparison is memory used in bytes.
 
-image:167Memory.png[image]
+image:images/167speed.png[image]
+
+image:images/167Memory.png[image]
 
 === Annotation binding