docs: update libraries-bom (#140)

Author: anguillanneuf

README.md

@@ -18,7 +18,7 @@ If you are using Maven with a BOM, add this to your pom.xml file:
  <dependency>
  <groupId>com.google.cloud</groupId>
  <artifactId>libraries-bom</artifactId>
- <version>2.9.0</version>
+ <version>4.4.1</version>
  <type>pom</type>
  <scope>import</scope>
  </dependency>