GDScript: Fix "Identifier not found" error when accessing inner class from inside #8284

Job	Run time
📊 Static checks / Code style, file formatting, and docs	1m 27s
🍏 iOS / Template (target=template_release)	29m 38s
🍎 macOS / Editor (target=editor, tests=yes)	47m 2s
🍎 macOS / Template (target=template_release)	34m 53s
🐧 Linux / Editor w/ Mono (target=editor)	5m 13s
🐧 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)	51m 5s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	59m 47s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	36m 38s
🐧 Linux / Template w/ Mono (target=template_release)	34m 42s
🐧 Linux / Minimal template (target=template_release, everything disabled)	25m 7s
🌐 Web / Template (target=template_release)	31m 30s
🤖 Android / Template (target=template_release)	40m 21s
🏁 Windows / Editor (target=editor, tests=yes)	1h 41m 2s
🏁 Windows / Template (target=template_release)	49m 58s
🪲 Godot CPP / Build and test Godot CPP	11m 36s
	9h 19m 59s

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