Remove quotes as they are invalid syntax
minor #1652 Remove quotes as they are invalid syntax (sekjun9878)

This PR was squashed before being merged into the 2.0.x-dev branch (closes #1652).

Discussion
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Remove quotes as they are invalid syntax

When using Composer, the quotes result in the error message

```
[UnexpectedValueException]
Could not parse version constraint '~2.0@dev': Invalid version string "'~2.0@dev'"
```

I know this is minor, but copy-paste convenience :)

Commits
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d731615 Remove quotes as they are invalid syntax