Revert "Drop delete of index during deploy"

This reverts commit 90fcf2a3fcc18dba665e63739ccd35602367dd84.

script/prep-release.sh

@@ -82,5 +82,8 @@ cat ../netboot.xyz-sha256-checksums.txt
 mv ../netboot.xyz-sha256-checksums.txt .
 cd ../..
 
+# delete index.html so that we don't overwrite existing content type
+rm src/index.html
+
 # copy iPXE src code into build directory
 cp -R src/* build/