Update elem-descriptionOfComponents.xml

Corrected the availability to say "not repeatable", see #149

tei/ead4/en/elem-descriptionOfComponents.xml

@@ -60,7 +60,7 @@
 	<div type="attributeusage"><p>Use <att>descriptionOfComponentsType</att> to identify the format or level of descriptive detail used in this <gi>descriptionOfComponents</gi>. </p>
 <p>Use <att>descriptionOfComponentsTypeEncoding</att> in <gi>control</gi> to specify the source or rules for values supplied in <att>descriptionOfComponentsType</att>.</p></div>	
 	<div type="availability">
-		<p>Optional, repeatable</p>
+		<p>Optional, not repeatable</p>
 	</div>
 	<div type="examples">
 		<egXML xmlns="http://www.tei-c.org/ns/Examples">