Remove snap badge from README

[sabau]

Remove reference to Snap Builds, they should be built on Gaia

• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added a relevant changelog entry: clog add [section] [stanza] [message]

• rereviewed Files changed in the github PR explorer

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[sabau]

I would remove also the scripts if it's ok @alessio and make a follow up in gaia to move Snap over there

[codecov]

Codecov Report

Merging #4614 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4614      +/-   ##
==========================================
- Coverage   53.64%   53.62%   -0.02%     
==========================================
  Files         260      260              
  Lines       16176    16176              
==========================================
- Hits         8677     8675       -2     
- Misses       6853     6855       +2     
  Partials      646      646