Fix: Change $eq to _eq in the failing test.

[shahzadlone]

Relevant issue(s)

Resolves #575

Description

Fix the broken test on develop.

Tasks

• I made sure the code is well commented, particularly hard-to-understand areas.
• I made sure the repository-held documentation is changed accordingly.
• I made sure the pull request title adheres to the conventional commit style (the subset used in the project can be found in tools/configs/chglog/config.yml).
• I made sure to discuss its limitations such as threats to validity, vulnerability to mistake and misuse, robustness to invalidation of assumptions, resource requirements, ...

How has this been tested?

make test

Specify the platform(s) on which this was tested:

• Manjaro Linux on WSL2

[codecov]

Codecov Report

Merging #576 (528ecb7) into develop (b16bf3a) will increase coverage by 0.10%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #576      +/-   ##
===========================================
+ Coverage    56.88%   56.98%   +0.10%     
===========================================
  Files          121      121              
  Lines        14221    14243      +22     
===========================================
+ Hits          8089     8116      +27     
+ Misses        5418     5413       -5     
  Partials       714      714              

Impacted Files	Coverage Δ
query/graphql/planner/sum.go	81.69% <100.00%> (+6.89%)	⬆️