Fix dev docs typo

[MisRob]

Summary

Fixes a tiny typo in the documentation for new strings syntax (discovered here).

I think the intention was rather:

const { myCoolString$, stringWithArgument$ } = commonStringsModule;

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[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.0b13.dev0_git.547.g2efab3b8.pex
Windows Installer (EXE)	kolibri-0.16.0b13.dev0+git.547.g2efab3b8-unsigned.exe
Debian Package	kolibri_0.16.0b13.dev0+git.547.g2efab3b8-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.0b13.dev0+git.547.g2efab3b8-0.4.0.dmg
Android Package (APK)	kolibri-0.16.0b13.dev0+git.547.g2efab3b8-0.1.0-debug.apk
TAR file	kolibri-0.16.0b13.dev0+git.547.g2efab3b8.tar.gz
WHL file	kolibri-0.16.0b13.dev0+git.547.g2efab3b8-py2.py3-none-any.whl