fix old import URL in comments

[maito1201]

now if I use import command at github.com/doug-martin/goqu/v9/adapters/

It doesn't work as below.

$ go get github.com/doug-martin/goqu/v9/adapters/postgres
go: downloading github.com/doug-martin/goqu v1.0.0
go: downloading github.com/doug-martin/goqu/v9 v9.13.0
go: downloading github.com/doug-martin/goqu v5.0.0+incompatible
go get: module github.com/doug-martin/goqu/v9@upgrade found (v9.13.0), but does not contain package github.com/doug-martin/goqu/v9/adapters/postgres

every implementation is fixed but some comments are still old links.

[codecov]

Codecov Report

Merging #286 (5f092c1) into master (ff08a24) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #286   +/-   ##
=======================================
  Coverage   96.77%   96.77%           
=======================================
  Files          60       60           
  Lines        3319     3319           
=======================================
  Hits         3212     3212           
  Misses         91       91           
  Partials       16       16           

Flag	Coverage Δ
unittests	96.77% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
database.go	94.06% <ø> (ø)
sql_dialect.go	100.00% <ø> (ø)
sqlgen/delete_sql_generator.go	100.00% <ø> (ø)
sqlgen/expression_sql_generator.go	100.00% <ø> (ø)
sqlgen/insert_sql_generator.go	100.00% <ø> (ø)
sqlgen/select_sql_generator.go	100.00% <ø> (ø)
sqlgen/truncate_sql_generator.go	100.00% <ø> (ø)
sqlgen/update_sql_generator.go	100.00% <ø> (ø)

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