CLEANUP: qpack: fix copy-paste typo in value Huffman debug string

CLEANUP: qpack: fix copy-paste typo in value Huffman debug string

In qpack_decode_fs(), when decoding a literal field line with a literal
value, the debug message mistakenly printed "[name huff ...]" instead of
"[value huff ...]" after a successful Huffman decoding of the value string.

This is a harmless copy-paste typo from the field name decoding block
just above, fix it to prevent confusion when debugging QPACK streams.

Should be easily backported to all versions to ease further modifications
into the QPACK code.