Small VFS doc fix #306

Job	Run time
build	3m 39s
test (BoxingTests.Kernel)	1m 44s
test (Cosmos.Compiler.Tests.TypeSystem.Kernel)	2m 21s
test (Cosmos.Compiler.Tests.Bcl.Kernel)	2m 55s
test (Cosmos.Compiler.Tests.Bcl.System.Kernel)	3m 39s
test (Cosmos.Compiler.Tests.Exceptions.Kernel)	1m 46s
test (Cosmos.Compiler.Tests.MethodTests.Kernel)	1m 40s
test (Cosmos.Compiler.Tests.SingleEchoTest.Kernel)	1m 42s
test (Cosmos.Kernel.Tests.Fat.Kernel)	3m 2s
test (Cosmos.Kernel.Tests.IO.Kernel)	1m 53s
test (SimpleStructsAndArraysTest.Kernel)	1m 46s
test (Cosmos.Kernel.Tests.DiskManager.Kernel)	1m 42s
test (GraphicTest.Kernel)	2m 3s
test (NetworkTest.Kernel)	59s
test (AudioTests.Kernel)	4m 5s
test (MemoryOperationsTest.Kernel)	2m 6s
test (ProcessorTests.Kernel)	1m 37s
	38m 39s

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