chore: switch default keyring backend

[rahulghangas]

• closes Use the file keyring backend as a default #405
• manually test that default value is switched

[codecov-commenter]

Codecov Report

Merging #1141 (7bb4bba) into main (c16d6e7) will increase coverage by 0.28%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1141      +/-   ##
==========================================
+ Coverage   47.98%   48.27%   +0.28%     
==========================================
  Files          71       71              
  Lines        3995     3994       -1     
==========================================
+ Hits         1917     1928      +11     
+ Misses       1909     1899      -10     
+ Partials      169      167       -2     

Impacted Files	Coverage Δ
pkg/shares/share_splitting.go	73.56% <100.00%> (+13.33%)	⬆️
x/blob/types/payforblob.go	80.35% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[cmwaters]

LGTM.

I also built it locally and can see it has changed:

Flags:
  -h, --help                     help for keys
      --keyring-backend string   Select keyring's backend (os|file|test) (default "file")
      --keyring-dir string       The client Keyring directory; if omitted, the default 'home' directory will be used
      --output string            Output format (text|json) (default "text")