/usr/lib/ is in thunderbird-locale-pa 1:24.4.0+build1-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/thunderbird/
/usr/lib/thunderbird/distribution/
/usr/lib/thunderbird/distribution/searchplugins/
/usr/lib/thunderbird/distribution/searchplugins/locale/
/usr/lib/thunderbird/distribution/searchplugins/locale/pa-IN/
/usr/lib/thunderbird/distribution/searchplugins/locale/pa-IN/bing.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/pa-IN/amazondotcom.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/pa-IN/eBay.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/pa-IN/yahoo.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/pa-IN/aol-web-search.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/pa-IN/twitter.xml
/usr/lib/thunderbird/distribution/searchplugins/locale/pa-IN/wikipedia.xml
/usr/lib/thunderbird-addons/
/usr/lib/thunderbird-addons/extensions/
/usr/lib/thunderbird-addons/extensions/langpack-pa-IN@thunderbird.mozilla.org.xpi