Update roslyn to 5.6.0 - #1959

  2 files  ±0    2 suites  ±0   9m 10s ⏱️ - 1m 4s
664 tests ±0  562 ✅ ±0  102 💤 ±0  0 ❌ ±0 
751 runs  ±0  649 ✅ ±0  102 💤 ±0  0 ❌ ±0 

Results for commit 33b80b7. ± Comparison against earlier commit 82e6ef5.