fd/fmt: Don't depend on fmtlib

We still support fmtlib expressions but our code doesn't use fmtlib for
anything now.

Change-Id: I186d23deaba3bbc5450f69e3d94f1812e2dec708
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/fd/fmt.cpp b/test/fd/fmt.cpp
index 9448fed..397fcae 100644
--- a/test/fd/fmt.cpp
+++ b/test/fd/fmt.cpp
@@ -33,7 +33,7 @@
         buf.append(FMT_COMPILE("{}"), std::string(2050, 'a'));
         EXPECT_EQ(4106, fd.lseek(0, Whence::Cur));
 
-        buf.append(FMT_STRING("hi\n"));
+        buf.append("hi\n");
         EXPECT_EQ(4106, fd.lseek(0, Whence::Cur));
     }
     EXPECT_EQ(4109, fd.lseek(0, Whence::Cur));