[libc] Remove unused variable

GitOrigin-RevId: 2f1c037bbdc4a949e83466d6b315002d71c67731
diff --git a/src/__support/str_to_float.h b/src/__support/str_to_float.h
index b2347a9..7c26720 100644
--- a/src/__support/str_to_float.h
+++ b/src/__support/str_to_float.h
@@ -746,11 +746,9 @@
 
   if (isdigit(*src) || *src == DECIMAL_POINT) { // regular number
     int base = 10;
-    char exponentMarker = 'e';
     if (is_float_hex_start(src, DECIMAL_POINT)) {
       base = 16;
       src += 2;
-      exponentMarker = 'p';
       seenDigit = true;
     }
     char *newStrEnd = nullptr;