fix filename extension of included graphics

Author: nolda

P5/Source/Guidelines/en/AI-AnalyticMechanisms.xml

@@ -1216,7 +1216,7 @@ oks	book	NOUN	_	_	2	obj	_	_
       index for the (unrepresented) root node is 0.</p>
     <p>A graphical rendition of this example is given below in terms of an
       annotated dependency graph.</p>
-    <p><graphic url="Images/dependency1.jpg"/></p>
+    <p><graphic url="Images/dependency1.png"/></p>
     <p>In this directed graph, the labelled arcs each connect a
       <term>dependent</term> node and its <term>head</term> node. The arc labels
       indicate the type of the dependency relation. A somewhat special relation
@@ -1264,7 +1264,7 @@ oks	book	NOUN	_	_	2	obj	_	_
     <p>As can be seen from the graphical rendition of this example below, there
       are dependent nodes with multiple arcs, pointing to more than one head
       node.</p>
-    <p><graphic url="Images/dependency2.jpg"/></p>
+    <p><graphic url="Images/dependency2.png"/></p>
     <p>For convenience, those additional arcs are rendered as curves.</p>
     <p>The above example may be encoded as follows:
       <egXML xmlns="http://www.tei-c.org/ns/Examples">