Fix how multiplication is displayed (#27825)

Asterisk character is used for italicizing by the styling engine. It needs to be escaped with a backslash.

docs/sources/features/datasources/postgres.md

@@ -144,7 +144,7 @@ Macro example | Description
 *`$__timeFilter(dateColumn)`* | Will be replaced by a time range filter using the specified column name. For example, *dateColumn BETWEEN '2017-04-21T05:01:17Z' AND '2017-04-21T05:06:17Z'*
 *`$__timeFrom()`* | Will be replaced by the start of the currently active time selection. For example, *'2017-04-21T05:01:17Z'*
 *`$__timeTo()`* | Will be replaced by the end of the currently active time selection. For example, *'2017-04-21T05:06:17Z'*
-*`$__timeGroup(dateColumn,'5m')`* | Will be replaced by an expression usable in a GROUP BY clause. For example, *(extract(epoch from dateColumn)/300)::bigint*300*
+*`$__timeGroup(dateColumn,'5m')`* | Will be replaced by an expression usable in a GROUP BY clause. For example, *(extract(epoch from dateColumn)/300)::bigint\*300*
 *`$__timeGroup(dateColumn,'5m', 0)`* | Same as above but with a fill parameter so missing points in that series will be added by Grafana and 0 will be used as the value.
 *`$__timeGroup(dateColumn,'5m', NULL)`* | Same as above but NULL will be used as value for missing points.
 *`$__timeGroup(dateColumn,'5m', previous)`* | Same as above but the previous value in that series will be used as fill value. If no value has been seen yet, NULL will be used (only available in Grafana 5.3+).