chore: fixing syntax throwing an error

[uncleempty]

It is there to fix a small problem, introduced in one of the previous PRs.

As per the customer report, it shows syntax errors when trying to run the command from the SDK readme:

./vendor/bin/qtisdk render -df --source /Users/*/Downloads/i6422d9afb42b32279aab31294164637a8/qti.xml --flavour goldilocks > ./qti.html
PHP Parse error:  syntax error, unexpected token "{" in /Users/*/Downloads/test/taoApi/vendor/qtism/qtism/src/qtism/cli/Render.php on line 283

Which is pretty logical, since variable interpolation won't work outside of "string context".

[wazelin]

Ooh. This is pretty bad.
Thank you for the fix, @uncleempty!

Luckily, this issue concerns only the CLI part of the library. Merging and releasing should be sufficient. No need to deploy this anywhere.

[bugalot]

Thanks for this! You might also want to consider upgrading wp-cli as in the following PR (that I never merged)
CC @wazelin / @uncleempty #408

[bugalot]

as well as the usage of relative paths in that exact command, which would be nice :)