Updates the backend error messages more clearly (#5605)

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**What type of PR is this:**

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/kind cleanup

**What does this PR do / why we need it:**

Updates the backend error message to indicate that Docker or Podman
should be installed.

**Which issue(s) this PR fixes:**
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N/A

**PR acceptance criteria:**

- [X] Unit test

- [X] Integration test

- [X] Documentation

**How to test changes / Special notes to the reviewer:**

Signed-off-by: Charlie Drage <charlie@charliedrage.com>

pkg/devfile/image/image.go

@@ -104,5 +104,5 @@ func selectBackend() (Backend, error) {
 	if _, err := lookPathCmd(dockerCmd); err == nil {
 		return NewDockerCompatibleBackend(dockerCmd), nil
 	}
-	return nil, errors.New("no backend found")
+	return nil, errors.New("odo requires either Podman or Docker to be installed in your environment. Please install one of them and try again.")
 }