Automated Feature Gates Update (#475)

Auto-generated PR from daily feature gates check

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Noah Gundotra <ngundotra@users.noreply.github.com>

Author: github-actions[bot]

app/utils/feature-gate/featureGates.json

@@ -71,7 +71,7 @@
     "version": "v2.1.6",
     "testnetActivationEpoch": 746,
     "devnetActivationEpoch": 813,
-    "mainnetActivationEpoch": null,
+    "mainnetActivationEpoch": 750,
     "title": "Add TowerSync instruction",
     "description": "Enable new voting instruction",
     "simd_link": "https://github.com/solana-foundation/solana-improvement-documents/blob/main/proposals/0138-deprecate-legacy-vote-instructions.md"