Use Lambda in Snapshot1Test.java

This is a follow-on fix to RT-35197. Due to some issues with the tools, the automated lambda changes for the following file was reverted:

tests/system/src/test/java/javafx/scene/Snapshot1Test.java

I will attach a patch for this (basically the same as was attached to the previous issue). It was generated using NB, and excluding (reverting) the two places that cannot be turned into a lambda expression.