doc: fix buf.readUIntBE, buf.readUIntLE examples

The documentation describing the output from the examples for
buf.readUIntBE and buf.readUIntLE were switched in terms of what the
code would actually output. This patch addresses this by switching the
two lines of example code to be in the same order as the functions are
listed earlier in the documentation.

PR-URL: https://github.com/nodejs/node/pull/8240
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>

doc/api/buffer.md

@@ -1644,10 +1644,10 @@ Examples:
 const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
 
 // Prints: 1234567890ab
-console.log(buf.readUIntLE(0, 6).toString(16));
+console.log(buf.readUIntBE(0, 6).toString(16));
 
 // Prints: ab9078563412
-console.log(buf.readUIntBE(0, 6).toString(16));
+console.log(buf.readUIntLE(0, 6).toString(16));
 
 // Throws an exception: RangeError: Index out of range
 console.log(buf.readUIntBE(1, 6).toString(16));