Bump MSRV to 1.70

[mtreinish]

This commit bumps the MSRV for rustworkx in 0.15.0 to 1.70.0. This enables us to use GATs (see #1143) and also enables to update some of our dependencies which require newer versions of rust to compile.

[IvanIsCoding]

I think you are installing 1.7 instead of 1.70

[coveralls]

Pull Request Test Coverage Report for Build 8516439127

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 96.503%

---

Files with Coverage Reduction	New Missed Lines	%
src/shortest_path/all_pairs_bellman_ford.rs	6	95.53%
<!--	Total:	6		-->

Totals
Change from base Build 8513980155:	-0.03%
Covered Lines:	17136
Relevant Lines:	17757

---

💛 - Coveralls