remove a duplicated include
remove a duplicated include

Detection of string_view type (whether it's std or Abseil)
is done in googletest/include/gtest/internal/gtest-port.h
with GTEST_INTERNAL_HAS_STRING_VIEW.

antidotcb/googletest,google/googletest,gianricardo/googletest,google/googletest,google/googletest,antidotcb/googletest,gianricardo/googletest,antidotcb/googletest,antidotcb/googletest,google/googletest,gianricardo/googletest