[remote_transmitter] add missing underline (#5238)

Author: aanban

components/remote_transmitter.rst

@@ -193,6 +193,7 @@ companies.
 .. _remote_transmitter-transmit_beo4:
 
 ``remote_transmitter.transmit_beo4`` **Action**
+***********************************************
 
 This :ref:`action <config-action>` sends a B&O Beo4 infrared protocol code to a remote transmitter.
 
@@ -380,6 +381,7 @@ Configuration variables:
 .. _remote_transmitter-transmit_gobox:
 
 ``remote_transmitter.transmit_gobox`` **Action**
+************************************************
 
 This :ref:`action <config-action>` sends a command to a Go-Box via the IR transmitter.