Reduce max input size in parser fuzzer

Still seeing stack overflows for $$$$$x style input, let's reduce
the input size limit further...

sapi/fuzzer/fuzzer-parser.c

@@ -26,7 +26,7 @@
 #include "fuzzer-sapi.h"
 
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
-	if (Size > 7 * 1024) {
+	if (Size > 6 * 1024) {
 		/* Large inputs have a large impact on fuzzer performance and may cause stack overflows,
 		 * but are unlikely to be necessary to reach new codepaths. */
 		return 0;

sapi/fuzzer/generate_parser_corpus.php

@@ -9,7 +9,7 @@ $it = new RecursiveIteratorIterator(
 $corpusDir = __DIR__ . '/corpus/parser';
 @mkdir($corpusDir);
 
-$maxLen = 7 * 1024;
+$maxLen = 6 * 1024;
 foreach ($it as $file) {
     if (!preg_match('/\.phpt$/', $file)) continue;
     $code = file_get_contents($file);