Fix typo in build/README.md (#10307)

build/README.md

@@ -4,7 +4,7 @@ This folder contains some files that we use to build the `mattermost-server` usi
 
 PRs opened against the `mattermost-server` repository will use the file called `Jenkinsfile.pr`
 
-The `Dockerfile` in this folder (`Dockerfile.buildenv`) is the build environment for our current builds you can find the docker image to downalod [here](https://hub.docker.com/r/mattermost/mattermost-build-server/tags/) or build your own.
+The `Dockerfile` in this folder (`Dockerfile.buildenv`) is the build environment for our current builds you can find the docker image to download [here](https://hub.docker.com/r/mattermost/mattermost-build-server/tags/) or build your own.