Revert "Use "gfxstream" namespace"

Revert submission 2513870-gfxstream-namespace-2

Reason for revert: This breaks the MacOS gfxstream build.

Reverted changes: /q/submissionid:2513870-gfxstream-namespace-2
Bug: 276321260

Change-Id: I6ab589a1308cce5fd467f8e57c158a8179aeb133

system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp

diff --git a/system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp b/system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp
index dc18142..375bc6e 100644
--- a/system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp
+++ b/system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp
@@ -9,9 +9,6 @@
 #include <string_view>
 #include <thread>
 
-namespace gfxstream {
-namespace vk {
-
 using ::testing::A;
 using ::testing::ElementsAre;
 using ::testing::Eq;
@@ -724,7 +721,4 @@
 
     EXPECT_DEATH({ (void)stream.allocBuffer(kTestBufferSize); }, "")
         << "allocBuffer() should not be called while previous data is being flushed";
-}
-
-}  // namespace vk
-}  // namespace gfxstream
+}
\ No newline at end of file