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

python/educational-python/course-creator-python/resources/META-INF/plugin.xml

@@ -1,4 +1,4 @@
-<idea-plugin version="2">
+<idea-plugin>
   <id>com.jetbrains.edu.coursecreator.python</id>
   <name>Course Creator for PyCharm Edu</name>
   <version>2.0.3</version>

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>

python/educational-python/student-python/resources/META-INF/plugin.xml

@@ -1,5 +1,5 @@
 <!--suppress XmlUnboundNsPrefix -->
-<idea-plugin version="2">
+<idea-plugin>
   <id>com.jetbrains.python.edu.interactivelearning.python</id>
   <name>Educational plugin for PyCharm</name>
   <version>2.0.4</version>