chore: enable unbound-method eslint rule

[rix0rrr]

Unbound method calls using this are likely to have unintended effects.

Here is an example with static methods, but the same thing applies to object methods:

class Class {
  public static staticMethod() {
    this.otherStaticMethod()
  }

  public static otherStaticMethod() { }
}

// ✅ valid
Class.staticMethod();

// ❌ boom
const x = Class.staticMethod;
x();

When assigning a method to a variable, you need to take extra care and this linter rule is going to remind you.

---

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.41%. Comparing base (f925551) to head (dcc31df).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #165      +/-   ##
==========================================
- Coverage   84.60%   84.41%   -0.19%     
==========================================
  Files         198      198              
  Lines       35400    35401       +1     
  Branches     4569     4543      -26     
==========================================
- Hits        29951    29885      -66     
- Misses       5295     5373      +78     
+ Partials      154      143      -11     

Flag	Coverage Δ
suite.unit	84.41% <100.00%> (-0.19%)	⬇️

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