fixing missing include causing unknown 'unique_ptr' in legacy/gnupg/g10/keyid.cpp

[bitpick]

Getting a build issue on FC26 causes compiling error:

legacy/gnupg/g10/keyid.cpp:581:12: error: ‘unique_ptr’ is not a member of ‘std’
std::unique_ptrBotan::HashFunction rmd160(Botan::HashFunction::create_or_throw("RIPEMD-160"));

Fixed by including

[codecov]

Codecov Report

Merging #7 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master     #7   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          16     16           
  Lines         302    302           
=====================================
  Hits          302    302

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