update references to just compose (#1869)

#### What type of PR is this?

Change from Docker Compose references to just Compose

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Add one of the following kinds:
/kind bug
/kind cleanup
/kind documentation
/kind feature
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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:
<!--
*Automatically closes linked issue when PR is merged.
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>

script/test/fixtures/buildargs/README.md

@@ -1,4 +1,4 @@
-## Docker Compose Buildargs
+## Compose Buildargs
 
 ### Usage
 

script/test/fixtures/etherpad/README.md

@@ -1,4 +1,4 @@
-## Docker Compose Etherpad
+## Compose Etherpad
 
 Etherpad and Mariadb