Add missing include TLine.h

Exposed in build against ROOT 6.24 candidate.

added Build bug fix lhcb-lcg-dev4 labels

@rmatev I have added the lhcb-lcg-dev4 label to fix the build errors in https://lhcb-nightlies.web.cern.ch/logs/build/nightly/lhcb-lcg-dev4/1592/x86_64-centos7-gcc9-opt/Alignment/ but should be backwards compatible so can be picked up by RTA testing and merged

• [2021-03-23 00:20] Validation started with lhcb-lcg-dev4#1593
• [2021-03-24 00:30] Validation started with lhcb-head#2900
• [2021-03-24 00:32] Validation started with lhcb-lcg-dev4#1594
• [2021-03-24 01:33] Validation started with lhcb-head#2900

added lhcb-head label

I think this can be merged

approved this merge request

merged

mentioned in commit 9c36a937

removed lhcb-lcg-dev4 label

removed lhcb-head label

mentioned in issue Moore#263 (closed)