Remove "This function was added in Prometheus 2.0"
Since Prometheus documentation is versioned, do not write down that a
specific function was added in Prom 2.0, for consistency.
@@ -411,8 +411,6 @@ expression is to be evaluated.
`timestamp(v instant-vector)` returns the timestamp of each of the samples of
the given vector as the number of seconds since January 1, 1970 UTC.
-*This function was added in Prometheus 2.0*
-
## `vector()`
`vector(s scalar)` returns the scalar `s` as a vector with no labels.
