MINOR: Fix small typo in main README (#7779)

Fixed a small typo in the main README file ("They are also are printed" --> "They are also printed").

Reviewers: Manikumar Reddy <manikumar.reddy@gmail.com>

README.md

@@ -169,7 +169,7 @@ You can run checkstyle using:
     ./gradlew checkstyleMain checkstyleTest
 
 The checkstyle warnings will be found in `reports/checkstyle/reports/main.html` and `reports/checkstyle/reports/test.html` files in the
-subproject build directories. They are also are printed to the console. The build will fail if Checkstyle fails.
+subproject build directories. They are also printed to the console. The build will fail if Checkstyle fails.
 
 #### Spotbugs ####
 Spotbugs uses static analysis to look for bugs in the code.