docs: Remove double "the" in README
Excised an extraneous definite article in the install README.
How did we miss this in the review phase I wonder?
@@ -30,6 +30,6 @@ Select your preferred distribution or cloud service:
## Further information
-* The [the upgrading document](../Upgrading.md).
+* The [upgrading document](../Upgrading.md).
* The [developer guide](../Developer-Guide.md).
* The [runtime documentation](https://github.com/kata-containers/runtime/blob/master/README.md).
