content: change variable names in exported names article

It was confusing to some people that the article mentions Foo, FOO, and foo, when
the code example doesn't contain those names.

This replaces the foos with variations on Pi, which is the
constant used in the example.

Fixes golang/go#13045

Change-Id: I4ea572915dbd56a2fcbef6ea3691e1be397460cd
Reviewed-by: Brad Fitzpatrick <>
1 file changed