Fix missing confirmation in apt-upgrade in Docker build

[juhoinkinen]

apt-get upgrade was added in Docker build to ensure that system packages are up-to-date in the image in PR #707, but I did not add -y option to it, because it seemed unnecessary as the command worked while testing without it (and in this SO post the -y was concluded to be unnecessary, but the post was about apt-get update!)

However, it seems that when there is some packages to upgrade, then then the -y option is necessary. Without it the build fails:

#5 2.944 Calculating upgrade...
#5 3.091 The following packages will be upgraded:
#5 3.091   libssl1.1 openssl
#5 3.094 2 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
#5 3.094 Need to get 2413 kB of archives.
#5 3.094 After this operation, 4096 B disk space will be freed.
#5 3.094 Do you want to continue? [Y/n] Abort.
------
ERROR: failed to solve: executor failed running [/bin/bash -c apt-get update && apt-get upgrade && 	if [[ $optional_dependencies =~ "voikko" ]]; then 		apt-get install -y --no-install-recommends 			libvoikko1 			voikko-fi; 	fi && 	apt-get install -y --no-install-recommends rsync && 	rm -rf /var/lib/apt/lists/* /usr/include/*]: exit code: 1
Error: buildx failed with: ERROR: failed to solve: executor failed running [/bin/bash -c apt-get update && apt-get upgrade && 	if [[ $optional_dependencies =~ "voikko" ]]; then 		apt-get install -y --no-install-recommends 			libvoikko1 			voikko-fi; 	fi && 	apt-get install -y --no-install-recommends rsync && 	rm -rf /var/lib/apt/lists/* /usr/include/*]: exit code: 1

[sonarcloud]

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0.0% Duplication

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +3.85 🎉

Comparison is base (579701c) 95.81% compared to head (7762fe6) 99.67%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #711      +/-   ##
==========================================
+ Coverage   95.81%   99.67%   +3.85%     
==========================================
  Files          89       89              
  Lines        6380     6380              
==========================================
+ Hits         6113     6359     +246     
+ Misses        267       21     -246     

see 10 files with indirect coverage changes

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