Revert "Post match wait time is now a configuration variable."

This reverts commit 2809a75ed9cce6e6a38f903fb191b12acf2a7596.
Revert "Allow some time for posts to get matched to rivers before considering them for"

This reverts commit 30582e9a0fd0b16d18566d1f33080951296778e4.
Revert "hack: delay collection of rivers that a new post belongs to"

This reverts commit 78071d01362c7e8138136f620e8403936d4c5b4b.
replace sleepy hack with river_posts approach