[depr.capture.this] Replace "can" with "may".

This wording is describing permission, not capability, so should use "may".

Author: zygoloid

source/future.tex

@@ -53,7 +53,7 @@
 \pnum
 For compatibility with prior \Cpp{} International Standards,
 a lambda expression with \grammarterm{capture-default}
-\tcode{=}\iref{expr.prim.lambda.capture} can implicitly capture
+\tcode{=}\iref{expr.prim.lambda.capture} may implicitly capture
 \tcode{*this} by reference.
 \begin{example}
 \begin{codeblock}