Merge pull request #5752 from wled/remove_save_ram

remove unmaintained WLED_SAVE_RAM

On 8266, compiling with WLED_SAVE_RAM increases flash program size by 1.2KB, while reducing static RAM by 20 bytes only. Plus it reduces the size of the Segment::Transition struct by 48 bytes (from 80 to 32), by avoiding a separate palette for blending.

On the other side, the WLED_SAVE_RAM special code is not maintained (corner case, needs a special build flag to activate), and its largely untested with the latest codebase.