Fix Readme typo: providing --> provided (#253)

"Database support is providing using … "

Author: gruentee

README.md

@@ -39,7 +39,7 @@ $ pip install databases[mysql]
 $ pip install databases[sqlite]
 ```
 
-Driver support is providing using one of [asyncpg][asyncpg], [aiomysql][aiomysql], or [aiosqlite][aiosqlite].
+Driver support is provided using one of [asyncpg][asyncpg], [aiomysql][aiomysql], or [aiosqlite][aiosqlite].
 
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