Postpone to remove legacy mingw platform #7163

Job	Run time
Rubygems on Windows (3.2)	4m 24s
Rubygems on Windows (3.3)	3m 54s
Rubygems on Ubuntu (3.3)	1m 50s
Rubygems on macOS (3.2)	2m 14s
Rubygems on macOS (3.4)	3m 32s
Rubygems on macOS (3.3)	2m 24s
Rubygems on Ubuntu (truffleruby)	3m 35s
Rubygems on Windows (3.4)	3m 44s
Rubygems on Ubuntu (3.2)	2m 30s
Rubygems on Ubuntu (jruby)	6m 23s
Rubygems on Ubuntu (3.4)	4m 4s
All rubygems jobs pass	4s
	38m 38s

Provide feedback