Add "UNKNOWN" for "allow in any condition" IWLAN handover example

Bug 234095834 started to supported UNKNOWN in source of IWLAN
handover rules. While the rule syntax was added to include
"UNKNOWN" in source, the example in the same javadoc should
be updated as well to keep consistent.

Bug: 247170538
Test: m -j offline-sdk-docs
Change-Id: Ia566fc6f0e0fdc09cca963d298a1c44dcbee540a