HPCC-12092 DOCS: Error in Systems Admin. header

FIX HPCC-12092 DOCS: Error in Systems Admin. header
Spelling error

Signed-off-by: g-pan <greg.panagiotatos@lexisnexis.com>
Merge pull request #6347 from g-pan/H12092-SysAdmspErr

HPCC-12092 DOCS: Error in Systems Admin. header

Reviewed-By: Jim DeFabia <james.defabia@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>