[diff.cpp17] Remove stray linebreak.

Author: zygoloid

source/compatibility.tex

@@ -1829,7 +1829,7 @@
 \rSec2[diff.cpp17.lex]{\ref{lex}: lexical conventions}
 
 \ref{lex.key}
-\change New keywords.\\
+\change New keywords.
 \rationale Required for new features.
 The \tcode{requires} keyword is added
 to introduce constraints through a \grammarterm{requires-clause} or