tests: Correct testcase in script_tests.json for large number OP_EQUAL

Fix a test case that was passing correctly by accident, but not testing
the right thing. Reported by helo on IRC.

src/test/data/script_tests.json

@@ -349,7 +349,7 @@
 ["2147483647", "0x04 0xFFFFFF7F EQUAL", "P2SH,STRICTENC", "OK"],
 ["2147483648", "0x05 0x0000008000 EQUAL", "P2SH,STRICTENC", "OK"],
 ["549755813887", "0x05 0xFFFFFFFF7F EQUAL", "P2SH,STRICTENC", "OK"],
-["549755813888", "0x06 0xFFFFFFFF7F EQUAL", "P2SH,STRICTENC", "OK"],
+["549755813888", "0x06 0x000000008000 EQUAL", "P2SH,STRICTENC", "OK"],
 ["9223372036854775807", "0x08 0xFFFFFFFFFFFFFF7F EQUAL", "P2SH,STRICTENC", "OK"],
 ["-1", "0x01 0x81 EQUAL", "P2SH,STRICTENC", "OK", "Numbers are little-endian with the MSB being a sign bit"],
 ["-127", "0x01 0xFF EQUAL", "P2SH,STRICTENC", "OK"],