Fix wrong text shortening in some corner cases ('...' being longer than 2 chars)

[nroggeman-ledger]

Description

The goal of this PR is to fix text shortening (nbgl_textWrapOnNbLines()) in some corner cases ("..." being longer than 2 chars)

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 18 lines in your changes missing coverage. Please review.

Project coverage is 35.76%. Comparing base (603cf09) to head (8fa9f90).
Report is 68 commits behind head on API_LEVEL_21.

Files with missing lines	Patch %	Lines
lib_nbgl/src/nbgl_fonts.c	0.00%	18 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                @@
##           API_LEVEL_21     #781       +/-   ##
=================================================
- Coverage         60.19%   35.76%   -24.44%     
=================================================
  Files                12       13        +1     
  Lines              1726     1591      -135     
=================================================
- Hits               1039      569      -470     
- Misses              687     1022      +335     

Flag	Coverage Δ
unittests	35.76% <0.00%> (-24.44%)	⬇️

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