Fix doc typo in argument_matchers.rb #775

Job	Run time
Rubocop	34s
Ruby 2.7 (Windows)	3m 34s
Legacy Ruby Builds (2.1.9)	3m 39s
Ruby 2.6 (Windows)	3m 44s
Ruby 3.2	2m 52s
Legacy Ruby Builds (2.0)	1m 19s
Ruby 2.5 (Windows)	2m 40s
Ruby 3.1	2m 52s
Legacy Ruby Builds (1.9.3)	1m 54s
Ruby 3.0	3m 18s
Ruby 2.4 (Windows)	5m 9s
Legacy Ruby Builds (1.9.2)	2m 33s
Ruby 2.3 (Windows)	2m 33s
Ruby 2.7	3m 31s
Legacy Ruby Builds (1.8.7)	1m 49s
Ruby 2.2 (Windows)	2m 45s
Ruby 2.6	5m 6s
Legacy Ruby Builds (REE)	3m 49s
Ruby 2.5	4m 49s
Legacy Ruby Builds (JRuby 1.7)	4m 2s
Ruby 2.4	3m 46s
Legacy Ruby Builds (JRuby 1.7 1.8 mode)	5m 5s
Ruby 2.3	3m 31s
Legacy Ruby Builds (JRuby 9.1.17.0)	6m 6s
Ruby 2.2	3m 38s
Ruby ruby-head	1m 12s
Ruby jruby-9.2.13.0	7m 32s
Ruby 2.7 with diff-lcs 1.3	3m 49s
Ruby 2.7 with diff-lcs 1.4.3	4m 21s
	1h 41m 32s

Provide feedback