[intro.memory] Merge footnote on CHAR_BIT into main text

The footnote on `CHAR_BIT` is information relevant to the main
text of the corresponding paragraph, where it can usefully be
indexed.

Author: AlisdairM

source/basic.tex

@@ -3366,13 +3366,10 @@
 and the eight-bit code units of the Unicode
 \indextext{UTF-8}%
 UTF-8 encoding form
-and is composed of a contiguous sequence of
-bits,
-\begin{footnote}
-The number of bits in a byte is reported by the macro
-\tcode{CHAR_BIT} in the header \libheaderref{climits}.
-\end{footnote}
-the number of which is \impldef{bits in a byte}.
+and is composed of a contiguous sequence of bits,
+the number of which is \impldef{bits in a byte}
+and reported by the macro \libmacro{CHAR_BIT}
+in the header \libheaderref{climits}.
 The memory available to a \Cpp{} program consists of one or more sequences of
 contiguous bytes.
 Every byte has a unique address.