Fix error related to lighttpd MIME type handling

lighttpd wouldn't start, erroring with something like

    (../src/configfile.c.2449) include file not found:
/etc/lighttpd/mime-types.conf
    (../src/configfile.c.2256) source: /httpd.conf line: 10 pos: 0
parser failed somehow near here: (EOL)

This is because the alpine packaging for lighttpd has moved away from
including this file in the default setup [1]. It doesn't seem to be
needed anymore, so it can probably go.

[1]:
632d675ea8

Dockerfile

@@ -39,7 +39,6 @@ COPY sites/${SITE}/httpd.conf /httpd.conf
 COPY sites/${SITE}/_data/config.json /config.json
 
 RUN sed -i \
-	-e "s,@mimetypes@,/etc/lighttpd/mime-types.conf,g" \
 	-e "s,@python@,/usr/local/bin/python,g" \
 	-e  "s,@site@,/www,g" \
 	-e  "s,@cgibin@,/cgi-bin,g" \

sites/angestoepselt/httpd.conf

@@ -5,8 +5,6 @@ server.port = 80
 # See here: https://redmine.lighttpd.net/boards/2/topics/8382
 accesslog.filename = "/dev/fd/3"
 
-include "@mimetypes@"
-
 server.document-root = "@site@"
 index-file.names = ( "index.html" )
 

sites/coderdojo/httpd.conf

@@ -5,8 +5,6 @@ server.port = 80
 # See here: https://redmine.lighttpd.net/boards/2/topics/8382
 accesslog.filename = "/dev/fd/3"
 
-include "@mimetypes@"
-
 server.document-root = "@site@"
 index-file.names = ( "index.html" )