Minor cmake improvements for the emscripten build

[anutosh491]

Description

As Sylvain pointed out, these are ON by default and we can avoid having them here.

Type of change

Please tick all options which are relevant.

• Bug fix
• New feature
• Added/removed dependencies
• Required documentation updates

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.78%. Comparing base (2226ca0) to head (945228f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #337   +/-   ##
=======================================
  Coverage   81.78%   81.78%           
=======================================
  Files          20       20           
  Lines         950      950           
  Branches       87       87           
=======================================
  Hits          777      777           
  Misses        173      173           

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