Warnings when compiling the client app

[huitema]

Running with GCC, get the following warning:

 [ 78%] Building C object _deps/picotls-build/CMakeFiles/cli.dir/t/cli.c.o
/home/runner/work/quicrq/quicrq/build/_deps/picotls-src/t/cli.c: In function ‘handle_connection’:
/home/runner/work/quicrq/quicrq/build/_deps/picotls-src/t/cli.c:161:35: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result]
  161 |                             (void)write(sockfd, encbuf.base, encbuf.off);
      |                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/quicrq/quicrq/build/_deps/picotls-src/t/cli.c:170:33: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result]
  170 |                                 write(1, rbuf.base, rbuf.off);
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/quicrq/quicrq/build/_deps/picotls-src/t/cli.c:257:27: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result]
  257 |                     (void)write(sockfd, wbuf.base, wbuf.off);
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[huitema]

Fixed.