HPCC-11996 Read correct HTTP header for AcceptLanguage

The existing ESP does not read correct HTTP header for
AcceptLanguage. It returns the 'Accept' header due to a
bug.

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>
Merge pull request #6291 from wangkx/get_accept_lang

HPCC-11996 Read correct HTTP header for AcceptLanguage

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>