fix(fmt): do not print a second line when printing file to stdout

[gfanton]

address #2633

Avoid double printing newline when executing gno fmt without the -w (write) flag.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.39%. Comparing base (0e3c050) to head (bfab6b1).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2639      +/-   ##
==========================================
+ Coverage   54.99%   59.39%   +4.40%     
==========================================
  Files         595      574      -21     
  Lines       79775    75586    -4189     
==========================================
+ Hits        43872    44897    +1025     
+ Misses      32581    27292    -5289     
- Partials     3322     3397      +75     

Flag	Coverage Δ
contribs/gnofaucet	15.31% <ø> (+0.85%)	⬆️
gno.land	64.15% <ø> (ø)
gnovm	64.19% <100.00%> (+3.98%)	⬆️
misc/genstd	80.54% <ø> (ø)
misc/logos	20.23% <ø> (+2.85%)	⬆️
tm2	61.88% <ø> (+7.38%)	⬆️

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[thehowl]

There are failing tests; please address them