Fix ruff error due to use of .format() in diff.py

[devdanzin]

Newer versions of ruff started flagging an error in src/wily/commands/diff.py. This PR is the result of merely calling ruff with the --fix option:

src\wily\commands\diff.py:143:25: UP032 [*] Use f-string instead of `format` call
141 |                   if current > new:  # type: ignore
142 |                       metrics_data.append(
143 |                           "{0:n} -> \u001b[{2}m{1:n}\u001b[0m".format(
    |  _________________________^
144 | |                             current, new, BAD_COLORS[metric.measure]
145 | |                         )
    | |_________________________^ UP032
146 |                       )
147 |                   elif current < new:  # type: ignore
    |
    = help: Convert to f-string
src\wily\commands\diff.py:149:25: UP032 [*] Use f-string instead of `format` call
    |
148 |                       metrics_data.append(
149 |                           "{0:n} -> \u001b[{2}m{1:n}\u001b[0m".format(
    |  _________________________^
150 | |                             current, new, GOOD_COLORS[metric.measure]
151 | |                         )
    | |_________________________^ UP032
152 |                       )
153 |                   else:
    |
    = help: Convert to f-string

Found 2 errors.
[*] 2 potentially fixable with the --fix option.

This currently blocks #206.

[codecov-commenter]

Codecov Report

Merging #207 (00fb994) into master (8eb4416) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #207   +/-   ##
=======================================
  Coverage   95.46%   95.46%           
=======================================
  Files          26       26           
  Lines        1346     1346           
  Branches      287      287           
=======================================
  Hits         1285     1285           
  Misses         37       37           
  Partials       24       24           

Files Changed	Coverage Δ
src/wily/commands/diff.py	89.53% <ø> (ø)