Bump nokogiri from 1.13.6 to 1.15.5 in /docs #1035

Job	Run time
install-test-ubuntu-make	1m 54s
test-macos-make-release-shared	1m 12s
install-test-ubuntu-make-with-transcoder	5m 46s
test-macos-make-release-shared-with-transcoder	2m 37s
install-test-macos-make	1m 34s
test-macos-make-release-static	1m 16s
install-test-macos-make-with-transcoder	3m 48s
test-macos-make-release-static-with-transcoder	2m 52s
install-test-macos-xcode	5m 6s
test-macos-xcode-release-shared	4m 20s
install-test-macos-xcode-with-transcoder	9m 48s
test-macos-xcode-release-shared-with-transcoder	4m 44s
install-test-windows-make	2m 46s
test-macos-xcode-release-static	2m 36s
test-macos-xcode-release-static-with-transcoder	4m 47s
install-test-windows-make-with-transcoder	7m 14s
test-ubuntu-make-release-shared	1m 46s
install-test-windows-msvc	2m 19s
test-ubuntu-make-release-shared-with-transcoder	5m 13s
install-test-windows-msvc-with-transcoder	4m 22s
test-ubuntu-make-release-static	1m 57s
test-ubuntu-make-release-static-with-transcoder	4m 45s
test-windows-msvc-release-shared	2m 31s
test-windows-msvc-release-shared-with-transcoder	5m 54s
test-windows-msvc-release-static	2m 41s
test-windows-msvc-release-static-with-transcoder	6m 47s
test-windows-make-release-shared	2m 53s
test-windows-make-release-shared-with-transcoder	6m 37s
test-windows-make-release-static	3m 13s
test-windows-make-release-static-with-transcoder	6m 39s
	1h 59m 57s

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