Remove ensureCustomElements in esr 128
We added ensureCustomElements to the security panel in !1029 (merged). But after bugzilla 1803678 this method no longer exists and should not be needed, so we should drop it when we move to esr 128.
We added ensureCustomElements to the security panel in !1029 (merged). But after bugzilla 1803678 this method no longer exists and should not be needed, so we should drop it when we move to esr 128.