Fix various typos (#3312)

Found via `codespell -q 3 -S ./test/gtest -L "fo,pres,seh,wronly"`

include/fmt/chrono.h

@@ -1156,7 +1156,7 @@ void write_fractional_seconds(OutputIt& out, Duration d, int precision = -1) {
   }
 }
 
-// Format subseconds which are given as a floating point type with an appropiate
+// Format subseconds which are given as a floating point type with an appropriate
 // number of digits. We cannot pass the Duration here, as we explicitly need to
 // pass the Rep value in the chrono_formatter.
 template <typename Duration>

include/fmt/std.h

@@ -34,7 +34,7 @@
 // GCC 4 does not support FMT_HAS_INCLUDE.
 #if FMT_HAS_INCLUDE(<cxxabi.h>) || defined(__GLIBCXX__)
 #  include <cxxabi.h>
-// Android NDK with gabi++ library on some archtectures does not implement
+// Android NDK with gabi++ library on some architectures does not implement
 // abi::__cxa_demangle().
 #  ifndef __GABIXX_CXXABI_H__
 #    define FMT_HAS_ABI_CXA_DEMANGLE