[text analytics] update sdk version in readme
@@ -76,7 +76,7 @@ This table shows the relationship between SDK versions and supported API version
|SDK version|Supported API version of service
|-|-
|5.0.0 - Latest GA release (can be installed by removing the `--pre` flag)| 3.0
-|5.1.0b3 - Latest release (beta)| 3.0, 3.1-preview.2, 3.1-preview.3
+|5.1.0b4 - Latest release (beta)| 3.0, 3.1-preview.2, 3.1-preview.3
### Authenticate the client
