Remove now unsuitable arch attributes in equinox.core.sdk feature

Now that the o.e.equinox.security.win32 fragment is architecture
independent (because it is implemented through JNA) restricting it to
one arch when including it in features is not necessary anymore.

This was forgotten in PR
#564

features/org.eclipse.equinox.core.sdk/feature.xml

@@ -74,13 +74,11 @@
    <plugin
          id="org.eclipse.equinox.security.win32"
          os="win32"
-         arch="x86_64"
          version="0.0.0"/>
 
    <plugin
          id="org.eclipse.equinox.security.win32.source"
          os="win32"
-         arch="x86_64"
          version="0.0.0"/>
 
    <plugin