Adjust memory size in MTLTexurePool.m

There is a question asked on PR - https://github.com/openjdk/jdk/pull/2403
for file - src/java.desktop/macosx/native/libawt_lwawt/java2d/metal/MTLTexurePool.m

This means that a 4k display with a narrower aspect ratio wouldn't fit (assuming there ever were to be such a thing). What would happen if you encountered a screen that was, say, 4k * 2.5K?

Please address it on PR https://github.com/openjdk/jdk/pull/2403
If no code change is needed, you can close this bug.