fix zipSlip

[jukzi]

https://github.com/eclipse-jdt/eclipse.jdt.core/security/code-scanning/34

[sratz]

This causes

java.lang.IllegalArgumentException: Bad zip entry: overrides/..ROOT...override in C:\<snip>\plugins\org.eclipse.jem_2.1.0.v202307260438.jar
	at org.eclipse.jdt.internal.core.JarPackageFragmentRoot.computeChildren(JarPackageFragmentRoot.java:155)
	at org.eclipse.jdt.internal.core.JavaProjectElementInfo.initializePackageNames(JavaProjectElementInfo.java:276)
	at org.eclipse.jdt.internal.core.JavaProjectElementInfo.getProjectCache(JavaProjectElementInfo.java:244)
	at org.eclipse.jdt.internal.core.JavaProject.getProjectCache(JavaProject.java:2396)
	at org.eclipse.jdt.internal.core.JavaProjectElementInfo.newNameLookup(JavaProjectElementInfo.java:333)
	at org.eclipse.jdt.internal.core.JavaProject.newNameLookup(JavaProject.java:2808)
	at org.eclipse.jdt.internal.core.JavaProject.newNameLookup(JavaProject.java:2802)
	at org.eclipse.jdt.internal.core.JavaProject.newNameLookup(JavaProject.java:2820)
	at org.eclipse.jdt.internal.core.JavaProject.newNameLookup(JavaProject.java:2812)
	at org.eclipse.jdt.internal.core.JavaProject.findType(JavaProject.java:1707)
	at org.eclipse.jdt.internal.core.JavaProject.findType(JavaProject.java:1608)
	at org.eclipse.pde.internal.core.util.PDEJavaHelper.isOnClasspath(PDEJavaHelper.java:111)
	...

No idea what this file does, but it appears to have some use:
https://github.com/eclipse-jeetools/webtools.javaee/tree/master/plugins/org.eclipse.jem/overrides

.. per se is not dangerous. The .. should probably be ../ (or ..\), to prevent path traversal attacks.