Make `public` parse similar to `export`

I expect `public` to parse similarly to `export`, but that doesn't seem to be the case.

On Julia 1.11.0-rc3 (and all other versions I have tested):
```
julia> begin
export foo
end

julia> begin
public foo
end
ERROR: ParseError:
# Error @ REPL[2]:2:12
begin
public foo
# └─┘ ── Expected `end`
Stacktrace:
[1] top-level scope
@ none:1

julia> :(export foo)
:(export foo)

julia> :(public foo)
ERROR: ParseError:
# Error @ REPL[4]:1:10
:(public foo)
# └─┘ ── Expected `)`
Stacktrace:
[1] top-level scope
@ none:1
```

Is this a bug or mistaken expectations?