Fix parentheses in mstatus SD description

Repeated parentheses were not escaped, so they were not displayed correctly.

Signed-off-by: Jordan Carlin <jordanmcarlin@gmail.com>

src/machine.adoc

@@ -1135,7 +1135,7 @@ additional microarchitectural bits might be maintained in the extension
 to further reduce context save and restore overhead.
 
 The SD bit is read-only and is set when either the FS, VS, or XS bits
-encode a Dirty state (i.e., SD=((FS==11) OR (XS==11) OR (VS==11))). This
+encode a Dirty state (i.e., SD=\((FS==11) OR (XS==11) OR (VS==11))). This
 allows privileged code to quickly determine when no additional context
 save is required beyond the integer register set and `pc`.