fix: remove mseUpdating flag

[xiaoyuhen]

fix: remove mseUpdating flag

Description

No need to use mseUpdating flag

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[codecov-io]

Codecov Report

Merging #63 into master will increase coverage by 0.06%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #63      +/-   ##
==========================================
+ Coverage   52.02%   52.08%   +0.06%     
==========================================
  Files         123      123              
  Lines        1705     1703       -2     
==========================================
  Hits          887      887              
+ Misses        818      816       -2

Impacted Files	Coverage Δ
packages/griffith-mp4/src/mse/controller.js	0% <0%> (ø)	⬆️

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