fix(lang): Remove fsharp references

[jmgrosen]

I accidentally added some fsharp references back in my rebase of #554. This commit removes them.

Checklist

• Any new parsing code was already published, integrated, and merged into Semgrep. DO NOT MERGE THIS PR BEFORE THE SEMGREP INTEGRATION WORK WAS COMPLETED.
• Change has no security implications (otherwise, ping the security team)