Tidy up jruby spec for std error splitter #725

Job	Run time
Rubocop	21s
Rubocop	21s
Ruby 2.7 (Windows)	2m 37s
Ruby 2.7 (Windows)	2m 37s
Ruby 3.3	1m 41s
Ruby 3.3	1m 41s
Ruby 2.6 (Windows)	2m 6s
Ruby 2.6 (Windows)	2m 6s
Legacy Ruby Builds (2.1.9)	41s
Legacy Ruby Builds (2.1.9)	41s
Ruby 3.2	1m 31s
Ruby 3.2	1m 31s
Ruby 2.5 (Windows)	2m 6s
Ruby 2.5 (Windows)	2m 6s
Legacy Ruby Builds (2.0)	41s
Legacy Ruby Builds (2.0)	41s
Ruby 3.1	1m 30s
Ruby 3.1	1m 30s
Ruby 2.4 (Windows)	2m 6s
Ruby 2.4 (Windows)	2m 6s
Legacy Ruby Builds (1.9.3)	32s
Legacy Ruby Builds (1.9.3)	32s
Ruby 3.0	1m 51s
Ruby 3.0	1m 51s
Ruby 2.3 (Windows)	1m 49s
Ruby 2.3 (Windows)	1m 49s
Legacy Ruby Builds (1.9.2)	36s
Legacy Ruby Builds (1.9.2)	34s
Ruby 2.2 (Windows)	2m 0s
Ruby 2.2 (Windows)	2m 0s
Ruby 2.7	50s
Ruby 2.7	2m 2s
Legacy Ruby Builds (1.8.7)	34s
Legacy Ruby Builds (1.8.7)	34s
Legacy Ruby Builds (REE)	35s
Legacy Ruby Builds (REE)	35s
Ruby 2.6	59s
Ruby 2.6	3m 4s
Ruby 2.5	2m 55s
Ruby 2.5	2m 55s
Legacy Ruby Builds (JRuby 1.7)	42s
Legacy Ruby Builds (JRuby 1.7)	42s
Legacy Ruby Builds (JRuby 1.7 1.8 mode)	34s
Legacy Ruby Builds (JRuby 1.7 1.8 mode)	34s
Ruby 2.4	1m 32s
Ruby 2.4	1m 32s
Legacy Ruby Builds (JRuby 9.1.17.0)	44s
Legacy Ruby Builds (JRuby 9.1.17.0)	44s
Ruby 2.3	1m 42s
Ruby 2.3	1m 42s
Ruby 2.2	2m 12s
Ruby 2.2	2m 12s
Ruby ruby-head	30s
Ruby ruby-head	30s
Ruby jruby-9.2.13.0	1m 46s
Ruby jruby-9.2.13.0	1m 46s
Ruby 2.7 with diff-lcs 1.3	1m 59s
Ruby 2.7 with diff-lcs 1.3	1m 59s
Ruby 2.7 with diff-lcs 1.4.3	2m 2s
Ruby 2.7 with diff-lcs 1.4.3	2m 2s
	1h 26m 43s

Provide feedback