Update README.md

[Joannis]

The readme has a broken example snippet for running queries which is extremely confusing if you try to use it.
The result of this omission results in trying to run a query which leads users to use a String overload rather than the PostgresQuery overload which is not only SQL injection vulnerable but also returns an EventLoopFuture<PostgresResult>

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.37%. Comparing base (5d817be) to head (24a6809).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #541      +/-   ##
==========================================
- Coverage   61.39%   61.37%   -0.02%     
==========================================
  Files         125      125              
  Lines       10149    10149              
==========================================
- Hits         6231     6229       -2     
- Misses       3918     3920       +2     

see 2 files with indirect coverage changes

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