HPCC-9451 Docs:Clear Perm. Cache

Fix HPCC-9451 Clear Permission Cache
Document the new Clear Permission Cache
button in the Admin/File Scopes area of
ECLWatch.

Signed-off-by: g-pan <greg.panagiotatos@lexisnexis.com>
Merge pull request #4537 from g-pan/H9451-Cache

HPCC-9451 Docs:Clear Perm. Cache

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>