Extremely trivial typo fix (devcontainers#299)

Author: jshorty

_implementors/json_reference.md

@@ -76,7 +76,7 @@ When creating or working with a dev container, you may need different commands t
 
 | Property | Type  | Description |
 |:------------------|:------------|:------------|
-| `initializeCommand` | string,<br>array,<br>object | A command string or list of command arguments to run on the **host machine** before the container is created. .<br /><br /> ⚠️ The command is run wherever the source code is located on the host. For cloud services, this is in the cloud.<br><br>Note that the array syntax will execute the command without a shell. You can [learn more](#formatting-string-vs-array-properties) about formatting string vs array vs object properties. |
+| `initializeCommand` | string,<br>array,<br>object | A command string or list of command arguments to run on the **host machine** before the container is created.<br /><br /> ⚠️ The command is run wherever the source code is located on the host. For cloud services, this is in the cloud.<br><br>Note that the array syntax will execute the command without a shell. You can [learn more](#formatting-string-vs-array-properties) about formatting string vs array vs object properties. |
 | `onCreateCommand` 🏷️ | string,<br>array,<br>object | This command is the first of three (along with `updateContentCommand` and `postCreateCommand`) that finalizes container setup when a dev container is created. It and subsequent commands execute **inside** the container immediately after it has started for the first time.<br /><br> Cloud services can use this command when caching or prebuilding a container. This means that it will not typically have access to user-scoped assets or secrets.<br><br>Note that the array syntax will execute the command without a shell. You can [learn more](#formatting-string-vs-array-properties) about formatting string vs array vs object properties. |
 | `updateContentCommand` 🏷️ | string,<br>array,<br>object  | This command is the second of three that finalizes container setup when a dev container is created. It executes inside the container after `onCreateCommand` whenever new content is available in the source tree during the creation process.<br><br />It will execute at least once, but cloud services will also periodically execute the command to refresh cached or prebuilt containers. Like cloud services using `onCreateCommand`, it can only take advantage of repository and org scoped secrets or permissions.<br><br>Note that the array syntax will execute the command without a shell. You can [learn more](#formatting-string-vs-array-properties) about formatting string vs array vs object properties. |
 | `postCreateCommand` 🏷️ | string,<br>array,<br>object | This command is the last of three that finalizes container setup when a dev container is created. It happens after `updateContentCommand` and once the dev container has been assigned to a user for the first time.<br><br />Cloud services can use this command to take advantage of user specific secrets and permissions.<br><br>Note that the array syntax will execute the command without a shell. You can [learn more](#formatting-string-vs-array-properties) about formatting string vs array vs object properties. |