Update README.md

Fixed sentence which had 'set manually' accidentally repeated.

Author: thomasmulvaney

README.md

@@ -178,7 +178,7 @@ in the `Configuration` section.
 
 Bower will skip some interactive and analytics operations if it finds a `CI` environmental variable set to `true`. You will find that the `CI` variable is already set for you on many continuous integration servers, e.g., [CircleCI](https://circleci.com/docs/environment-variables#basics) and [Travis-CI](http://docs.travis-ci.com/user/ci-environment/#Environment-variables).
 
-You may try to set manually set `CI` variable manually before running your Bower commands. On Mac or Linux, `export CI=true` and on Windows `set CI=true`
+You may try to set the `CI` variable manually before running your Bower commands. On Mac or Linux, `export CI=true` and on Windows `set CI=true`
 
 ### Interactive configuration