Incorrect indentation in sample discovery templates in docs/discovery.md

[dssinger]

The examples for "Six Button KeypadLinc" and "Setting Switches as Lights" are incorrectly indented - the discovery_entities line in each one (and everything under it) should be indented two spaces so that the examples can be copied verbatim into the configuration file

[krkeegan]

These example were replaced in 9a2979a by discovery_overrides. Which is contained in docs/discovery_customization_config.md. Which is included in the next release.