Bump MSRV

Author: fjarri

.github/workflows/umbral-pre.yml

@@ -27,7 +27,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.70.0 # MSRV
+          - 1.81.0 # MSRV
           - stable
         target:
           - wasm32-unknown-unknown
@@ -45,7 +45,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.70.0 # MSRV
+          - 1.81.0 # MSRV
           - stable
         target:
           - thumbv7em-none-eabi
@@ -63,7 +63,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.70.0 # MSRV
+          - 1.81.0 # MSRV
           - stable
     steps:
       - uses: actions/checkout@v2
@@ -79,7 +79,7 @@ jobs:
       matrix:
         include:
           - target: x86_64-unknown-linux-gnu
-            rust: 1.70.0 # MSRV
+            rust: 1.81.0 # MSRV
           - target: x86_64-unknown-linux-gnu
             rust: stable