Fix Dockerfile

[norweeg]

Restores the two sed commands that I removed because I misread what they did. They replace the default document root (/var/www/html) with the environment variable APACHE_DOCUMENT_ROOT which is set to /var/www/filegator. No need to echo any apache config files. This fixes my mistake from #246 per https://hub.docker.com/_/php/

[codecov-commenter]

Codecov Report

Merging #254 (120460f) into master (c4a83e3) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #254   +/-   ##
=========================================
  Coverage     99.89%   99.89%           
  Complexity      368      368           
=========================================
  Files            25       25           
  Lines           944      944           
=========================================
  Hits            943      943           
  Misses            1        1           

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