Fix inline panel heading height

The `line-height` was added so that headings in the panels on the settings page had the same height as headings elsewhere, but the style applied everywhere :)

Before:

(Look at the "Unstarted Issues" heading)

![Screen_Shot_2015-12-15_at_17.39.46](/uploads/9dbea4c8b28e3c43bb5d4b5226d7a1ec/Screen_Shot_2015-12-15_at_17.39.46.png)

![Screen_Shot_2015-12-15_at_17.40.19](/uploads/97898418e9a66954c02e8a68b21c08b9/Screen_Shot_2015-12-15_at_17.40.19.png)

After:

![Screen_Shot_2015-12-15_at_17.40.45](/uploads/5748aba032889053dd778b39e96fa301/Screen_Shot_2015-12-15_at_17.40.45.png)

![Screen_Shot_2015-12-15_at_17.40.40](/uploads/20240cdc7a6d5665cd32556d1a0e6c1d/Screen_Shot_2015-12-15_at_17.40.40.png)

cc @skyruler 

cc @rspeicher 8.3 please!

See merge request !2106