Fix missing quote in fixtures.py

[emmyoop]

resolves # none
docs dbt-labs/docs.getdbt.com/#

Problem

Syntax error on fixture that wasn't caught as an error because parse doesn't catch it, only run.

Solution

Add missing quote.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[codecov]

Codecov Report

Merging #8324 (5815320) into main (f637092) will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #8324      +/-   ##
==========================================
- Coverage   86.28%   86.22%   -0.06%     
==========================================
  Files         174      174              
  Lines       25518    25518              
==========================================
- Hits        22017    22004      -13     
- Misses       3501     3514      +13     

see 3 files with indirect coverage changes

[QMalcolm]

Thank you for catching this!