Fix redirection of spec pages

[azeey]

🦟 Bug fix

Summary

Redirection of spec pages is not currently working because of some a logic error in the code. The /spec string is part of the url path not the search paramters, so the regex match was faling. The if block that handles the resulting new_loc variable was also in the wrong scope.

Test with:
http://sdformat.org/spec/?ver=1.12&elem=collision

http://localhost:3000/spec/?ver=1.12&elem=collision

Note that, testing redirection with nanoc live doesn't work all the time. If the / is missing right after spec, the server doesn't seem to add that, but testing with python3 -m http.server 3000 shows that the redirection works with and without the added /, i.e, both http://localhost:3000/spec/?ver=1.12&elem=collision and http://localhost:3000/spec?ver=1.12&elem=collision work.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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