Fix a useless use of a variable in void context warning #891

Job	Run time
Ruby ruby-head / Rack ~> 3.1	2m 17s
Ruby 3.3 / Rack ~> 3.1	2m 12s
Ruby 3.2 / Rack ~> 3.1	2m 13s
Ruby 3.1 / Rack ~> 3.1	2m 13s
Ruby 3.0 / Rack ~> 3.1	2m 12s
Ruby 2.7 / Rack ~> 3.1	2m 21s
Ruby 2.6 / Rack ~> 3.1	2m 45s
Ruby 3.3 / Rack ~> 3.1 --enable-frozen-string-literal	2m 14s
Ruby 3.3 / Rack ~> 3.0.0	2m 22s
Ruby 3.3 / Rack ~> 2.0	2m 20s
	23m 9s

Provide feedback