[implimits] Rephrase introductory sentence for list of quantities

Fixes ISO/CS comment (C++23 proof)

Author: jensmaurer

source/limits.tex

@@ -12,8 +12,8 @@
 or are unknown.
 
 \pnum
-The limits may constrain quantities
-that include those described below or others.
+The following list describes quantities that, among others, may be
+constrained by implementations.
 The bracketed number following each quantity is recommended
 as the minimum for that quantity.
 However, these quantities are only guidelines and do not determine compliance.