docs: #6065 shipped in v0.10.0, not v0.9.6

PR #6065 was intended to be backported to v0.9.6 to fix issue #6223.
However it appears to have not been backported:

 * https://github.com/hashicorp/nomad/blob/v0.9.6/client/allocrunner/taskrunner/task_runner.go#L1349-L1351
 * https://github.com/hashicorp/nomad/blob/v0.9.7/client/allocrunner/taskrunner/task_runner.go#L1349-L1351

The fix was included in v0.10.0:

 * https://github.com/hashicorp/nomad/blob/v0.10.0/client/allocrunner/taskrunner/task_runner.go#L1363-L1370

CHANGELOG.md

@@ -146,6 +146,7 @@ BUG FIXES:
  * client: Fixed a bug in client fingerprinting on 32-bit nodes [[GH-6239](https://github.com/hashicorp/nomad/issues/6239)]
  * client: Fixed a bug where completed allocations may re-run after client restart [[GH-6216](https://github.com/hashicorp/nomad/issues/6216)]
  * client: Fixed failure to start if another client is already running with the same data directory [[GH-6348](https://github.com/hashicorp/nomad/pull/6348)]
+ * client: Fixed a panic that may occur when an `nomad alloc exec` is initiated while process is terminating [[GH-6065](https://github.com/hashicorp/nomad/issues/6065)]
  * devices: Fixed a bug causing CPU usage spike when a device is detected [[GH-6201](https://github.com/hashicorp/nomad/issues/6201)]
  * drivers: Allowd user-defined environment variable keys to contain dashes [[GH-6080](https://github.com/hashicorp/nomad/issues/6080)]
  * driver/docker: Set gc image_delay default to 3 minutes [[GH-6078](https://github.com/hashicorp/nomad/pull/6078)]
@@ -178,7 +179,6 @@ BUG FIXES:
 
  * core: Fixed a bug where scheduler may schedule an allocation on a node without required drivers [[GH-6227](https://github.com/hashicorp/nomad/issues/6227)]
  * client: Fixed a bug where completed allocations may re-run after client restart [[GH-6216](https://github.com/hashicorp/nomad/issues/6216)] [[GH-6207](https://github.com/hashicorp/nomad/issues/6207)]
- * client: Fixed a panic that may occur when an `nomad alloc exec` is initiated while process is terminating [[GH-6065](https://github.com/hashicorp/nomad/issues/6065)]
  * devices: Fixed a bug causing CPU usage spike when a device is detected [[GH-6201](https://github.com/hashicorp/nomad/issues/6201)]
  * drivers: Fixed port mapping for docker and qemu drivers [[GH-6251](https://github.com/hashicorp/nomad/pull/6251)]
  * drivers/docker: Fixed a case where a `nomad alloc exec` would never time out [[GH-6144](https://github.com/hashicorp/nomad/pull/6144)]