x/pkgsite: function does not appear in table of contents

[stamblerre]

The function Expect appears on the page https://pkg.go.dev/github.com/onsi/gomega?tab=doc#Expect, but it is not listed in the table of contents.

[go101]

It is shown under "type Assertion", though I also feel this is some confused.

[julieqiu]

/cc @dmitshur for input - this is also how it is currently displayed on godoc.org.

/cc @fflewddur @Joanne881107

[go101]

This problem has been discussed before: #28006

[dmitshur]

Per comments above, Expect is considered to be a "factory function" for Assertion, so it's displayed underneath it.

The code for this is in go/doc (see #39813 (comment)). I don't see anything to do here, so let's close this. We can use #39813 as the tracking issue for considering changes to the "factory function" behavior.