Fix removing icons from README.md

Author: CherkashinSergey

README.md

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 # pg_variables - session variables with various types
 
+[![Build Status](https://travis-ci.org/postgrespro/pg_variables.svg?branch=master)](https://travis-ci.org/postgrespro/pg_variables)
+[![codecov](https://codecov.io/gh/postgrespro/pg_variables/branch/master/graph/badge.svg)](https://codecov.io/gh/postgrespro/pg_variables)
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+
 ## Introduction
 
 The **pg_variables** module provides functions to work with variables of various