LibWeb: Correct generated image and ratio-only replaced sizing #33352

Job	Run time
Linux, x86_64, Sanitizer, Clang / CI	14m 51s
Linux, arm64, Sanitizer, Clang / CI	35m 6s
Linux, x86_64, Release, GNU / CI	5m 0s
Linux, x86_64, All_Debug, Clang / CI	2m 59s
Windows, x86_64, Sanitizer, ClangCL / CI	7m 29s
macOS, arm64, Sanitizer, Clang / CI	44m 37s
Linux, x86_64, Fuzzers, Clang / CI	3m 27s
	1h 53m 29s

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