Merge pull request #2700 from buildkite/fix-no-git-submodules-typo

fix: BUILDKIT -> BUILDKITE

Author: gilesgas

data/content/agent_attributes.yaml

@@ -210,7 +210,7 @@ attributes:
   desc: |
       Do not allow this agent to run arbitrary console commands.
 - name: no-git-submodules
-  env_var: BUILDKITE_NO_GIT_SUBMODULES, BUILDKIT_DISABLE_GIT_SUBMODULES
+  env_var: BUILDKITE_NO_GIT_SUBMODULES, BUILDKITE_DISABLE_GIT_SUBMODULES
   default_value: "false"
   required: false
   desc: |