[format.string.std] 'decimal radix separator' -> 'radix separator'.

The use of the word 'decimal' here is not intended to mean "only base
10", and so serves only to confuse the reader.

Author: zygoloid

source/utilities.tex

@@ -19900,7 +19900,7 @@
 \item
 For floating-point types, the locale-specific form
 causes the context's locale to be used
-to insert the appropriate digit group and decimal radix separator characters.
+to insert the appropriate digit group and radix separator characters.
 
 \item
 For the textual representation of \tcode{bool}, the locale-specific form