languages.yml: don't assume .conf is Apache

The assumption that `.conf` files are Apache is causing many projects to
be detected incorrectly as being primarily "ApacheConf".

The `.conf` extension is widely used by software; Apache accounts for
only a very tiny proportion of its overall use. The addition of `.conf`
for ApacheConf has resulted in projects which contain none (or almost
no) Apache config being marked as primarily containing it.

The problem was introduced by 18a3ef9e5e

lib/linguist/languages.yml

@@ -148,7 +148,6 @@ ApacheConf:
   - apache
   extensions:
   - .apacheconf
-  - .conf
   tm_scope: source.apache-config
   ace_mode: apache_conf