docs: Update loki-http-api.md (backport release-3.3.x) (#15740)

Co-authored-by: priyaggopa <priyag494949@gmail.com>

docs/sources/reference/loki-http-api.md

@@ -149,8 +149,7 @@ being returned.
 
 The API accepts several formats for timestamps:
 
-- An integer with ten or fewer digits is interpreted as a Unix timestamp in seconds.
-- More than ten digits are interpreted as a Unix timestamp in nanoseconds.
+- All epoch values will be interpreted as a Unix timestamp in nanoseconds.
 - A floating point number is a Unix timestamp with fractions of a second.
 - A string in `RFC3339` and `RFC3339Nano` format, as supported by Go's [time](https://pkg.go.dev/time) package.