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V, 4 bytes

Î4É 


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(Note the trailing space)

V is encoded in Latin1, where this is encoded like so:

00000000: ce34 c920                                .4. 


Explanation

Î            " On every line
 4É&lt;space&gt;   " Prepend 4 spaces




Here's a solution that is also 4 bytes in UTF-8!

VG4&gt;

VG          " Select everything
   &gt;        " Indent
  4         " 4 times (with spaces)