Add pdf2htmlEX workaround to screenshotter in html_render_diff #1591

Job	Run time
build (ubuntu-24.04, clang-18)	4m 22s
build-test-downstream (ubuntu-24.04, clang-18)	2m 19s
build (ubuntu-24.04, gcc-14)	7m 15s
build (macos-13, clang-14)	5m 15s
build-test-downstream (ubuntu-24.04, gcc-14)	3m 0s
build-test-downstream (macos-13, clang-14)	1m 43s
build (macos-14, armv8-clang-14)	2m 28s
build-test-downstream (macos-14, armv8-clang-14)	1m 7s
build (windows-2022, msvc-1940)	5m 33s
build-test-downstream (windows-2022, msvc-1940)	2m 48s
docker (ubuntu-24.04, clang-18)	15s
test (ubuntu-24.04, clang-18)	4m 19s
test (ubuntu-24.04, gcc-14)	4m 17s
test (macos-13, clang-14)	3m 19s
test (macos-14, armv8-clang-14)	1m 49s
	49m 49s

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