Remove input files argument to target

[jonahwilliams]

Description

These are not really useful and mostly clutters up the API. Was only used by linux and windows copy rules, that was replaced with the artifact source.

[codecov]

Codecov Report

Merging #39701 into master will increase coverage by 0.71%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master   #39701      +/-   ##
==========================================
+ Coverage   56.27%   56.98%   +0.71%     
==========================================
  Files         194      194              
  Lines       18676    18632      -44     
==========================================
+ Hits        10509    10618     +109     
+ Misses       8167     8014     -153

Flag	Coverage Δ
#flutter_tool	56.98% <77.77%> (+0.71%)	⬆️

Impacted Files	Coverage Δ
...utter_tools/lib/src/build_system/targets/dart.dart	4.68% <0%> (-71.88%)	⬇️
...lutter_tools/lib/src/build_system/targets/ios.dart	4.25% <0%> (-74.47%)	⬇️
...er_tools/lib/src/build_system/targets/windows.dart	94.11% <100%> (+0.36%)	⬆️
...utter_tools/lib/src/build_system/build_system.dart	92.55% <100%> (ø)	⬆️
...tter_tools/lib/src/build_system/targets/linux.dart	94.44% <100%> (+0.32%)	⬆️
...ter_tools/lib/src/build_system/targets/assets.dart	87.27% <100%> (ø)	⬆️
...tter_tools/lib/src/build_system/targets/macos.dart	47.61% <75%> (ø)	⬆️
...ckages/flutter_tools/lib/src/commands/version.dart	4.34% <0%> (-89.14%)	⬇️
... and 34 more

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[jonahwilliams]

Accidentally merged this (rolled back), don't talk and type!