Remove note about night sky in PhysicalSkyMaterial #4

Job	Run time
📊 Static checks / Code style, file formatting, and docs	1m 8s
🍏 iOS / Template (target=template_release)	10m 20s
🍎 macOS / Editor (target=editor, tests=yes)	35m 32s
🤖 Android / Template (target=template_release)	31m 12s
🐧 Linux / Editor w/ Mono (target=editor)	39m 37s
🍎 macOS / Template (target=template_release)	21m 25s
🐧 Linux / Editor with doubles and GCC sanitizers (target=editor, tests=yes, dev_build=yes, scu_build=yes, precision=double, use_asan=yes, use_ubsan=yes, linker=gold)	49m 18s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	35m 3s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	24m 56s
🏁 Windows / Editor (target=editor, tests=yes)	50m 9s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	30m 18s
🌐 Web / Template w/o threads (target=template_release, threads=no)	25m 23s
🏁 Windows / Template (target=template_release)	40m 4s
🐧 Linux / Template w/ Mono (target=template_release)	27m 29s
🐧 Linux / Minimal template (target=template_release, everything disabled)	14m 26s
🪲 Godot CPP / Build and test Godot CPP	7m 35s
	7h 23m 55s

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