Fix compatibility renderer load of compressed layered `GL_TEXTURE_2D_ARRAY` #30539

Job	Run time
📊 Static checks / Code style, file formatting, and docs	26s
🍏 iOS / Template (target=template_release)	2m 29s
🐧 Linux / Editor w/ Mono (target=editor)	5m 41s
🍎 macOS / Editor (target=editor, tests=yes)	4m 14s
🐧 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)	18m 58s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	6m 36s
🍎 macOS / Template (target=template_release)	3m 1s
🤖 Android / Template (target=template_release)	4m 11s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	8m 13s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	4m 9s
🏁 Windows / Editor (target=editor, tests=yes)	9m 51s
🐧 Linux / Template w/ Mono (target=template_release)	2m 22s
🏁 Windows / Template (target=template_release)	8m 14s
🌐 Web / Template w/o threads (target=template_release, threads=no)	4m 17s
🐧 Linux / Minimal template (target=template_release, everything disabled)	2m 35s
🪲 Godot CPP / Build and test Godot CPP	7m 12s
	1h 32m 29s

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