[test] Tweak test to not check for any warnings at all

09b043c didn't do the trick, probably because some of the text is
going to stdout and some to stderr. Just don't check for warnings at
all in this test, at least for now.

rdar://problem/42271414, again.

Author: jrose-apple

test/Driver/Dependencies/only-skip-once.swift

@@ -4,8 +4,6 @@
 
 // RUN: cd %t && %target-swiftc_driver -driver-show-job-lifecycle -output-file-map %t/output-file-map.json -incremental main.swift file1.swift file2.swift -j1 2>&1 | %FileCheck -check-prefix=CHECK-INITIAL %s
 
-// CHECK-INITIAL-NOT: warning
-// CHECK-INITIAL: Queuing (initial):
 // CHECK-INITIAL: Job finished: {compile: main.o <= main.swift}
 // CHECK-INITIAL: Job finished: {compile: file1.o <= file1.swift}
 // CHECK-INITIAL: Job finished: {compile: file2.o <= file2.swift}
@@ -15,7 +13,6 @@
 // RUN: cd %t && %target-swiftc_driver -driver-show-job-lifecycle -output-file-map %t/output-file-map.json -incremental main.swift file1.swift file2.swift -j1 2>&1 | %FileCheck -check-prefix=CHECK-REBUILD %s
 
 // We should skip the main and file1 rebuilds here, but we should only note skipping them _once_
-// CHECK-REBUILD: Queuing (initial):
 // CHECK-REBUILD: Job finished: {compile: file2.o <= file2.swift}
 // CHECK-REBUILD: Job skipped: {compile: main.o <= main.swift}
 // CHECK-REBUILD: Job skipped: {compile: file1.o <= file1.swift}