Botched the changeset comment:

The ETCS markers on the Gotthard railway (Switzerland) accidentally used railway:signal:train_protection:form=sign instead of railway:signal:train_protection:main:form=sign (with "main") as specified in osm.wiki/OpenRailwayMap/ETCS_Markers

This changeset fixes this mistake, which should allow the markers to be displayed properly by OpenRailwayMap (vector).