[7.4] [DOCS][Reporting] Adds info about using a custom reporting index (#54052)#54169

Merged

gchaps merged 1 commit intoelastic:7.4from gchaps:backport/7.4/pr-54052

Jan 7, 2020

+24

Commits on Jan 7, 2020

[DOCS][Reporting] Adds info about using a custom reporting index (elastic#54052 )
gchaps
committed