Update MSRV to 1.44.0

Because of a (transitive) dependency (bitvec 0.19.x) that needs at least
1.44.0, we also depend on that version as the MSRV.

Signed-off-by: Matthias Beyer <[email protected]>

Author: matthiasbeyer

.github/workflows/msrv.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.40.0
+          - 1.44.0
           - stable
           - beta
           - nightly
@@ -36,7 +36,7 @@ jobs:
     strategy:
       matrix:
         rust:
-          - 1.40.0
+          - 1.44.0
           - stable
           - beta
           - nightly