Xattr tests with FUSE-T are broken on CI

Since around September 2025 normal CI builds fail due to failing tests:
* https://github.com/cryptomator/jfuse/actions/runs/21290356808/job/61282028989
* https://github.com/cryptomator/jfuse/actions/runs/18088981928
* etc

It only happens on macOS runners. For testing the FUSE-T library installed via brew is used. The test suite fails on the `TestXattr` integrations test:
```
Error: MirrorIT$TestXattr.testSetxattr:231 Unexpected exception thrown: java.nio.file.FileSystemException: /var/folders/kg/7q73ww8s3llgyl61c9z_j5g40000gn/T/junit-8422338435824566285/mirror/xattr.txt: Error writing extended attribute 'attr1': Operation not permitted
Error: MirrorIT$TestXattr.testSetxattr:231 Unexpected exception thrown: java.nio.file.FileSystemException: /var/folders/kg/7q73ww8s3llgyl61c9z_j5g40000gn/T/junit-8422338435824566285/mirror/xattr.txt: Error writing extended attribute 'attr2': Operation not permitted
Error: MirrorIT$TestXattr.testSetxattr:231 Unexpected exception thrown: java.nio.file.FileSystemException: /var/folders/kg/7q73ww8s3llgyl61c9z_j5g40000gn/T/junit-8422338435824566285/mirror/xattr.txt: Error writing extended attribute 'attr3': Operation not permitted
Error: MirrorIT$TestXattr.testSetxattr:231 Unexpected exception thrown: java.nio.file.FileSystemException: /var/folders/kg/7q73ww8s3llgyl61c9z_j5g40000gn/T/junit-8422338435824566285/mirror/xattr.txt: Error writing extended attribute 'attr4': Operation not permitted
Error: MirrorIT$TestXattr.testSetxattr:231 Unexpected exception thrown: java.nio.file.FileSystemException: /var/folders/kg/7q73ww8s3llgyl61c9z_j5g40000gn/T/junit-8422338435824566285/mirror/xattr.txt: Error writing extended attribute 'attr5': Operation not permitted
```

Setting xattr.txt in the source directory of the mirror test fails due to insufficient permissions.