Avoid line break in goto-check options [blocks: #6776]

[tautschnig]

Just a C string formatting change: This will avoid having to write extra
code in the bash autocompletion generator.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #6775 (f1dd8db) into develop (310b60c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #6775   +/-   ##
========================================
  Coverage    76.90%   76.90%           
========================================
  Files         1590     1590           
  Lines       183970   183970           
========================================
  Hits        141485   141485           
  Misses       42485    42485           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 397fcbd...f1dd8db. Read the comment docs.