Fixed path in Homebrew SpatiaLite docs.

[adamchainz]

Trac ticket number

N/A

Branch description

Homebrew hasn’t used /usr/local for some time. I couldn’t find exactly which version changed that, but the 3.0.0 release notes (2021) mention that M1 Macs now support the location, so presumably before that.

This PR changes the recommended path to one that exists (tested on my mac) and covers the case where the install path is non-default.

Checklist

• This PR targets the main branch.
• The commit message is written in past tense, mentions the ticket number, and ends with a period.
• I have checked the "Has patch" ticket flag in the Trac system.
• I have added or updated relevant tests.
• I have added or updated relevant docs, including release notes if applicable.
• For UI changes, I have attached screenshots in both light and dark modes.

[adamchainz]

Hmm I can’t find clear evidence but it may be that Intel macs use /usr/local and M1 macs use /opt/homebrew. I only saw a passing reference on a stack overflow for a related spatialite install issue.

[adamzap]

@adamchainz I think you're correct: https://docs.brew.sh/Installation

[adamchainz]

Ah, the install docs. I should have know. Thanks Adam!

[nessita]

Looks good, thanks! Will merge once CI runs are completed.

[adamzap]

Thanks for the co-author credit here. Very generous to mention me in the commit message!