Fix RichTextLabel bottom margin for text clipping #37840

Job	Run time
📊 Static checks / Code style, file formatting, and docs	29s
🤖 Android / Editor (target=editor)	6m 6s
🐧 Linux / Editor w/ Mono (target=editor)	6m 14s
🤖 Android / Template arm32 (target=template_release, arch=arm32)	4m 40s
🐧 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)	19m 36s
🍎 macOS / Editor (target=editor, tests=yes)	4m 59s
🤖 Android / Template arm64 (target=template_release, arch=arm64)	5m 3s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	9m 3s
🍏 iOS / Template (target=template_release)	2m 15s
🍎 macOS / Template (target=template_release)	4m 36s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	11m 4s
🐧 Linux / Template w/ Mono (target=template_release)	2m 56s
🐧 Linux / Minimal template (target=template_release, everything disabled)	2m 35s
🏁 Windows / Editor (target=editor, tests=yes)	43m 44s
🏁 Windows / Template (target=template_release)	32m 19s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	6m 38s
🌐 Web / Template w/o threads (target=template_release, threads=no)	7m 34s
🪲 Godot CPP / Build and test Godot CPP	8m 15s
	2h 58m 6s

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