gm self-test: stop checking stdout and stderr

gm/tests/outputs/pipe-playback-failure/output-expected/stdout

Index: gm/tests/outputs/pipe-playback-failure/output-expected/stdout
diff --git a/gm/tests/outputs/pipe-playback-failure/output-expected/stdout b/gm/tests/outputs/pipe-playback-failure/output-expected/stdout
deleted file mode 100644
index dbb4dd8ad987f714a947740a8add08589e57cfde..0000000000000000000000000000000000000000
--- a/gm/tests/outputs/pipe-playback-failure/output-expected/stdout
+++ /dev/null
@@ -1,20 +0,0 @@
-GM: These configs will be run: 8888 565
-GM: reading expectations from JSON summary file gm/tests/inputs/json/identical-pixels.json
-GM: writing to gm/tests/outputs/pipe-playback-failure/output-actual/writePath
-GM: writing mismatches to gm/tests/outputs/pipe-playback-failure/output-actual/mismatchPath
-GM: writing images without expectations to gm/tests/outputs/pipe-playback-failure/output-actual/missingExpectationsPath
-GM: reading resources from resources
-GM: drawing... selftest1 [300 200]
-GM: Ran 1 GMs
-GM: ... over  2 configs ["8888", "565"]
-GM: ...  and  2 modes   ["", "pipe"]
-GM: ... so there should be a total of 4 tests.
-GM: Ran 4 tests: NoGpuContext=0 IntentionallySkipped=0 RenderModeMismatch=2 GeneratePdfFailed=0 ExpectationsMismatch=0 MissingExpectations=0 WritingReferenceImage=0
-GM: [*] 0 NoGpuContext:
-GM: [ ] 0 IntentionallySkipped:
-GM: [*] 2 RenderModeMismatch: 8888/selftest1-pipe 565/selftest1-pipe
-GM: [*] 0 GeneratePdfFailed:
-GM: [*] 0 ExpectationsMismatch:
-GM: [ ] 0 MissingExpectations:
-GM: [*] 0 WritingReferenceImage:
-GM: (results marked with [*] will cause nonzero return value)