Fix warning icon visibility on light themes #49

Job	Run time
📊 Static checks / Code style, file formatting, and docs	1m 12s
🍎 macOS / Editor (target=editor, tests=yes)	30m 36s
🍎 macOS / Template (target=template_release)	19m 47s
🤖 Android / Template (target=template_release)	31m 50s
🍏 iOS / Template (target=template_release)	10m 35s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	22m 38s
🌐 Web / Template w/o threads (target=template_release, threads=no)	22m 40s
🐧 Linux / Editor w/ Mono (target=editor)	38m 42s
🐧 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)	46m 7s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	34m 48s
🏁 Windows / Editor (target=editor, tests=yes)	50m 8s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	31m 20s
🏁 Windows / Template (target=template_release)	33m 46s
🐧 Linux / Template w/ Mono (target=template_release)	25m 35s
🐧 Linux / Minimal template (target=template_release, everything disabled)	14m 29s
🪲 Godot CPP / Build and test Godot CPP	7m 8s
	7h 1m 21s

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