Plugin descriptors: remove deprecated attribute idea-plugin@version (IDEA-163694)

python/educational-python/src/META-INF/IdeTipsAndTricks.xml

@@ -1,4 +1,4 @@
-<idea-plugin version="2">
+<idea-plugin>
     <extensions defaultExtensionNs="com.intellij">
         <tipAndTrick file="Welcome.html"/>
         <tipAndTrick file="MultipleProjects.html"/>

python/educational-python/src/META-INF/PyCharmEduPlugin.xml

@@ -1,4 +1,4 @@
-<idea-plugin version="2" xmlns:xi="http://www.w3.org/2001/XInclude">
+<idea-plugin xmlns:xi="http://www.w3.org/2001/XInclude">
   <!-- Components and extensions declared in this file work ONLY in Pycharm Educational Edition -->
 
   <application-components>