Remove legacy install files. (#184)

Co-authored-by: André L F S Bacci <[email protected]>

Author: alfsb

configure.php

@@ -635,8 +635,6 @@ function getFileModificationHistory(): array {
 // Notice how doing it this way results in generating less than half as many files.
 $infiles = array(
     'manual.xml.in',
-    'install-unix.xml.in',
-    'install-win.xml.in',
     'scripts/file-entities.php.in',
 );