Remove array_remove() for supporting PostgreSQL 9.2

[k1LoW]

Fix #251

Remove array_remove for supporting PostgreSQL 9.2.

[codecov]

Codecov Report

Merging #253 into master will decrease coverage by 0.80%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #253      +/-   ##
==========================================
- Coverage   68.89%   68.08%   -0.81%     
==========================================
  Files          22       22              
  Lines        3687     3694       +7     
==========================================
- Hits         2540     2515      -25     
- Misses        902      939      +37     
+ Partials      245      240       -5     

Impacted Files	Coverage Δ
drivers/postgres/postgres.go	76.97% <100.00%> (+0.39%)	⬆️
datasource/datasource.go	22.22% <0.00%> (-12.70%)	⬇️

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