Delete bug78987.phpt test (#14982)

This test fails over and over again every time we update the library or
because of small changes elsewhere. This leads to a cycle of test
failures and us bumping the values again. This test has little value so
I propose to just get rid of it.

Fixes GH-13795.

ext/fileinfo/tests/bug78987.phpt

@@ -1,40 +0,0 @@
---TEST--
-Bug #78987 High memory usage during encoding detection
---EXTENSIONS--
-fileinfo
---INI--
-memory_limit=512M
---FILE--
-<?php
-$finfo = new finfo(FILEINFO_MIME_TYPE);
-$minSize = 128 * 1024;
-$maxSize = 16 * 1024 * 1024;
-
-$map = array(
-	131072 => 10612736,
-	262144 => 10612736,
-	524288 => 12189696,
-	1048576 => 12709888,
-	2097152 => 14811136,
-	4194304 => 19009536,
-	8388608 => 25300992,
-	16777216 => 37883904,
-);
-for($size = $minSize; $size <= $maxSize; $size *= 2) {
-	$content = str_repeat('0', $size);
-
-	$finfo->buffer($content);
-
-	$m = memory_get_peak_usage(true);
-	printf("%-8d => %s\n", $size, $m <= $map[$size] ? "ok" : "$m");
-}
-?>
---EXPECT--
-131072   => ok
-262144   => ok
-524288   => ok
-1048576  => ok
-2097152  => ok
-4194304  => ok
-8388608  => ok
-16777216 => ok