pw_string: Remove implicit double promotions

Cherry-pick from https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/67422

Change-Id: I0c92d22e8941f4802abf574a794a989f9b4436a1

pw_string/type_to_string.cc

diff --git a/pw_string/type_to_string.cc b/pw_string/type_to_string.cc
index 3475b12..ab58a52 100644
--- a/pw_string/type_to_string.cc
+++ b/pw_string/type_to_string.cc
@@ -153,7 +153,7 @@
   if (std::isfinite(value) &&
       std::abs(value) <
           static_cast<float>(std::numeric_limits<int64_t>::max())) {
-    return IntToString<int64_t>(::round(value), buffer);
+    return IntToString<int64_t>(roundf(value), buffer);
   }
 
   // Otherwise, print inf or NaN, if they fit.