spec: clarify behavior of map size hint for make built-in
The spec already states that the precise behavior of the map size
hint provided to the make built-in is implementation-dependent.
Exclude requiring specific run-time behavior for maps.
(The current Go compiler does not panic if the size hint is negative
at run-time.)
Fixes #53219.
Change-Id: I2f3618bf9ba4ed921e18dc4f2273eaa770805bd7
Reviewed-on: https://go-review.googlesource.com/c/go/+/411919 Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Keith Randall <khr@golang.org>