Fix ABS and SIGN grammar

h2/src/docsrc/help/help.csv

@@ -3880,7 +3880,7 @@ ENVELOPE(X)
 "
 
 "Functions (Numeric)","ABS","
-ABS(numeric|interval)
+ABS( { numeric | interval } )
 ","
 Returns the absolute value of a specified value.
 The returned value is of the same data type as the parameter.
@@ -4216,7 +4216,7 @@ CALL SECURE_RAND(16)
 "
 
 "Functions (Numeric)","SIGN","
-SIGN(numeric|interval)
+SIGN( { numeric | interval } )
 ","
 Returns -1 if the value is smaller than 0, 0 if zero, and otherwise 1.
 ","