Update README to list 'compute' as part of the default capabilities

Signed-off-by: NKevin Klues <kklues@nvidia.com>

README.md

@@ -146,7 +146,7 @@ This option controls which driver libraries/binaries will be mounted inside the
 #### Possible values
 * `compute,video`, `graphics,utility` …: a comma-separated list of driver features the container needs.
 * `all`: enable all available driver capabilities.
-* *empty* or *unset*: use default driver capability: `utility`.
+* *empty* or *unset*: use default driver capability: `utility,compute`.
 
 #### Supported driver capabilities
 * `compute`: required for CUDA and OpenCL applications.