Update deprecated Handle instantiation method name

[djc]

No description provided.

[codecov]

Codecov Report

Merging #186 into master will increase coverage by 0.16%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #186      +/-   ##
==========================================
+ Coverage   75.25%   75.41%   +0.16%     
==========================================
  Files          23       23              
  Lines        5557     5557              
==========================================
+ Hits         4182     4191       +9     
+ Misses       1375     1366       -9

Impacted Files	Coverage Δ
quinn/src/lib.rs	59.59% <100%> (+1%)	⬆️
quinn-proto/src/packet.rs	80.96% <0%> (ø)	⬆️
quinn-proto/src/connection.rs	73.24% <0%> (+0.17%)	⬆️

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