Update NaSC to 0.7.3
Updated NaSC to 0.7.3 which includes dark theme support and multiple bug fixes.
- Fixed a bug that caused a crash during startup.
- Fixed a case where the ans and line tokens failed to parse.
- Support for dark themes.
- Share panes to MathB.in.
Test Plan: Tested 0.7.3 by running through the tutorial. Everything looked and functioned as expected.
Reviewers: Triage Team, JoshStrobl
Reviewed By: Triage Team, JoshStrobl
Differential Revision: https://dev.getsol.us/D9342