internal/frontend: update homepage example search
internal/frontend: update homepage example search

Added missing '#' to symbol search example.

Change-Id: Idaefac89becc0efbbd7b94e14a16de065e1eaa32
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/352049
Trust: Jamal Carvalho <e0195770807aa8c82b0b128d9c0423b5ad035172@golang.org>
Reviewed-by: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite