Fix trailing whitespace in header comments

[dboehmer]

In my case SQL::Translator creates SQL-files for SQLite with trailing whitespace in empty comment lines.

I suggest fixing that by removing the single space from $DEFAULT_COMMENT and prefixing any comments with the space again.

I hope that $DEFAULT_COMMENT is not too important or too widely used to be changed.

[codecov]

Codecov Report

Merging #113 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master    #113   +/-   ##
======================================
  Coverage    21.5%   21.5%           
======================================
  Files          71      71           
  Lines       19914   19914           
  Branches     5728    5728           
======================================
  Hits         4283    4283           
  Misses      14922   14922           
  Partials      709     709

Impacted Files	Coverage Δ
lib/SQL/Translator/Utils.pm	67.44% <100%> (ø)	⬆️

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