fix grammar error

Author: uinstinct

docs/docs/customize/deep-dives/mcp.mdx

@@ -14,7 +14,7 @@ Currently custom tools can be configured using the [Model Context Protocol](http
 MCP Servers can be added to hub Assistants using `mcpServers` blocks. You can explore available MCP server blocks [here](https://hub.continue.dev/explore/mcp).
 
 :::info
-MCP can only used in the **agent** mode.
+MCP can only be used in the **agent** mode.
 :::
 
 To set up your own MCP server, read the [MCP quickstart](https://modelcontextprotocol.io/quickstart) and then [create an `mcpServers` block](https://hub.continue.dev/new?type=block&blockType=mcpServers) or add the following to your [config file](./configuration.md):