Fix typo lalbe -> label in nyquistcircles recipe

[baggepinnen]

Summary

• The centers series in the nyquistcircles plot recipe used lalbe as the attribute name, which is not a Plots attribute.
• The documented "Center" label was silently dropped (and some Plots versions warn about the unknown attribute).

Test plan

• Manual smoke check via nyquistcircles(w, centers, radii); "Center" entry now appears in the legend.
• No source-level test coverage exists for plotting recipes; nothing automated to add.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.84%. Comparing base (14a7deb) to head (2bcad9b).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #145   +/-   ##
=======================================
  Coverage   91.84%   91.84%           
=======================================
  Files          20       20           
  Lines        3064     3064           
=======================================
  Hits         2814     2814           
  Misses        250      250           

Flag	Coverage Δ
unittests	91.84% <100.00%> (ø)

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