CLT input format field with expression generates spurius warning

```
URI prefix '${ return ["http' of '${ return ["http://edamontology.org/format_2330"];}
' not recognized, are you missing a $namespaces section?
```
``` cwl
#!/usr/bin/env cwl-runner
$namespaces:
edam: "http://edamontology.org/"
cwlVersion: v1.0
class: CommandLineTool
requirements:
InlineJavascriptRequirement: {}
doc: "Reverse each line using the `rev` command"
inputs:
input:
type: File
inputBinding: {}
format: |
${ return ["http://edamontology.org/format_2330"];}

outputs:
output:
type: File
outputBinding:
glob: output.txt
format: |
${return "http://edamontology.org/format_2330";}

baseCommand: rev
stdout: output.txt