update references to just compose (#1869)

#### What type of PR is this?

Change from Docker Compose references to just Compose

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#### What this PR does / why we need it:

Compose is an open format and we should not say "Docker Compose".

#### Which issue(s) this PR fixes:
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Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
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Fixes https://github.com/kubernetes/kompose/issues/1868

#### Special notes for your reviewer:

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

cmd/root.go

@@ -51,7 +51,7 @@ var (
 // RootCmd root level flags and commands
 var RootCmd = &cobra.Command{
 	Use:   "kompose",
-	Short: "A tool helping Docker Compose users move to Kubernetes",
+	Short: "A tool helping Compose users move to Kubernetes",
 	Long:  `Kompose is a tool to help users who are familiar with docker-compose move to Kubernetes.`,
 	Example: `  kompose --file compose.yaml convert
   kompose -f first.yaml -f second.yaml convert