Ensure legend shows subway/light rail train protection in view (#867)

The type of rail was taken into account for filtering the legend. The
legend only contains `railway = rail` features, so all of the subway and
light rail rail features on the map were not shown in the legend because
their keys did not match.

Tested in
http://localhost:8000/#view=15.58/40.736959/-74.164143&style=signals:
<img width="1427" height="1110" alt="image"
src="https://github.com/user-attachments/assets/e66a9ff2-8a09-46ba-afac-793d59fd7452"
/>

Author: hiddewie

proxy/js/legend.mjs

@@ -1789,7 +1789,6 @@ const legendData = {
       },
       'openrailwaymap_low-railway_line_high': {
         key: [
-          'feature',
           'state',
           'train_protection',
           'train_protection_construction',
@@ -1841,7 +1840,6 @@ const legendData = {
       },
       'high-railway_line_high': {
         key: [
-          'feature',
           'state',
           'train_protection',
           'train_protection_construction',