Remove mention of Bower from the README (PR 15390 follow-up)

Author: Snuffleupagus

README.md

@@ -90,7 +90,7 @@ be loaded by `pdf.js`. The PDF.js files are large and should be minified for pro
 ## Using PDF.js in a web application
 
 To use PDF.js in a web application you can choose to use a pre-built version of the library
-or to build it from source. We supply pre-built versions for usage with NPM and Bower under
+or to build it from source. We supply pre-built versions for usage with NPM under
 the `pdfjs-dist` name. For more information and examples please refer to the
 [wiki page](https://github.com/mozilla/pdf.js/wiki/Setup-pdf.js-in-a-website) on this subject.