Clarify xref to fmt spec

Co-authored-by: Rangi <[email protected]>

src/asm/rgbasm.5

@@ -395,7 +395,7 @@ Most of them return a string, however some of these functions actually return an
 .Ql %spec
 pattern replaced by interpolating the format
 .Ar spec
-.Pq c.f. Sx Symbol interpolation
+.Pq using the same syntax as Sx Symbol interpolation
 with its corresponding argument in
 .Ar args
 .Pq So %% Sc is replaced by the So % Sc character .