[Desktop Entry]
Type=Application
Encoding=UTF-8
Name=pycsw
Comment=pycsw catalog server
Categories=Application;Education;Geography;
Exec=firefox http://localhost/pycsw/tests/index.html
Icon=/var/www/html/pycsw/docs/_static/pycsw-logo.png
Terminal=false
StartupNotify=false
Categories=Education;Geography;

[Desktop Entry]
Type=Application
Encoding=UTF-8
Name=pycsw
Comment=pycsw catalog server
Exec=firefox http://localhost/pycsw/tests/index.html
Icon=/var/www/html/pycsw/docs/_static/pycsw-logo.png
Terminal=false
StartupNotify=false
Categories=Education;Geography;

Fix desktop file validation error.
Fix desktop file validation error.

`desktop-file-validate` reported:
```
etc/pycsw.desktop: warning: key "Encoding" in group "Desktop Entry" is deprecated
etc/pycsw.desktop: error: file contains multiple keys named "Categories" in group "Desktop Entry"
etc/pycsw.desktop: warning: value "Application;Education;Geography;" for key "Categories" in group "Desktop Entry" contains a deprecated value "Application"
```
The duplicate "Categories" key with the deprecated "Application" value is removed.
