Fix MASM dot-code to indicate it also works on x64

Author: nir9

docs/assembler/masm/dot-code.md

@@ -8,7 +8,9 @@ ms.assetid: 2b8c882c-c0d2-4fa3-8335-e6b12717a4f4
 ---
 # .CODE
 
-(32-bit MASM only.) When used with [.MODEL](dot-model.md), indicates the start of a code segment.
+Indicates the start of a code segment.
+
+When using 32-bit MASM, this should be used along with [.MODEL](dot-model.md).
 
 ## Syntax