docs: use build.source in the on-cluster build guide (knative#4059)

Author: gauron99

cmd/deploy_test.go

@@ -1695,7 +1695,7 @@ func TestDeploy_RemoteBuildURLPermutations(t *testing.T) {
 				// TODO: (enhancement) allow --source when running local deployment.
 				// Check that the local builder is invoked with a directive to use a
 				// git repo rather than the local filesystem if building is enabled and
-				// a url is provided.  For now it throws an error statign that source
+				// a url is provided.  For now it throws an error stating that source
 				// is only used when --remote
 				if url != "" && err == nil {
 					t.Fatal("error expected when deploying from local but provided --source")

docs/building-functions/on_cluster_build.md

@@ -113,10 +113,10 @@ git remote add origin git@github.com:my-repo/my-function.git
 4. Update the Function configuration in `func.yaml` to enable on cluster builds for the Git repository:
 ```yaml
 build:
-  git:
+  source:
     url: https://github.com/my-repo/my-function.git   # required, git repository with the function source code
-    revision: main                                    # optional, git revision to be used (branch, tag, commit)
-    # contextDir: myfunction                          # optional, needed only if the function is not located in the repository root folder
+    revision: main                                    # optional, git revision to build (branch, tag, commit)
+    # dir: myfunction                                 # optional, needed only if the function is not located in the repository root folder
   buildpacks: []
   builder: ""
   buildEnvs: []