Bug 1645417 [wpt PR 24131] - Pin version of html5lib used in html/tools/build.sh, a=testonly

Automatic update from web-platform-tests
Pin version of html5lib used in html/tools/build.sh (#24131)

See web-platform-tests/wpt#24059 (review)
--

wpt-commits: 0614cc3f735509e57e29fdc482e67565601bf12e
wpt-pr: 24131

Author: stephenmcgruer

testing/web-platform/tests/html/tools/build.sh

@@ -5,6 +5,8 @@ cd "${0%/*}"
 virtualenv -p python .virtualenv
 .virtualenv/bin/pip install genshi
 git clone https://github.com/html5lib/html5lib-python.git .virtualenv/html5lib && cd .virtualenv/html5lib || cd .virtualenv/html5lib && git pull
+# Pinned commit, to avoid html5lib from changing underneath us.
+git reset --hard d49afd350c06339a8c59299664b8a73a3b2c3f64
 git submodule update --init --recursive
 cd ../..
 .virtualenv/bin/pip install -e .virtualenv/html5lib