Signals: fix max buffer size default

[silesky]

MAX_BUFFER_SIZE wasn't being set properly.

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 83.68%. Comparing base (82bc27b) to head (fff66c9).

Files with missing lines	Patch %	Lines
packages/signals/signals/src/core/buffer/index.ts	60.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1233   +/-   ##
=======================================
  Coverage   83.68%   83.68%           
=======================================
  Files         219      219           
  Lines        5843     5843           
  Branches     1330     1332    +2     
=======================================
  Hits         4890     4890           
  Misses        953      953           

Flag	Coverage Δ
browser	92.22% <ø> (ø)
core	89.86% <ø> (ø)
node	87.93% <ø> (ø)

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