Temporarily remove half-baked v128.const parsing support

I added this in a37fbd8 and
7177c2d because a recent change in the
official WebAssembly tests [0] added some uses of `v128.const` outside
of the test/core/simd directory. This was even more recently fixed by
moving those uses into test/core/simd [1], so we don’t need this dummy
parsing code any more. I’ll bring it back if/when we get around to
properly implementing SIMD instructions.

[0] WebAssembly/spec#1597
[1] WebAssembly/spec#1610

lib/wasminna/ast_parser.rb

@@ -641,11 +641,7 @@ def parse_start
     NUMERIC_OPCODE_REGEXP =
       %r{
         \A
-        (
-          (?<type>[fi]) (?<bits>32|64)
-          |
-          (?<type>v) (?<bits>128)
-        ) \. (?<operation>.+)
+        (?<type>[fi]) (?<bits>32|64) \. (?<operation>.+)
         \z
       }x
 
@@ -745,7 +741,7 @@ def parse_numeric_instruction
 
       opcode.match(NUMERIC_OPCODE_REGEXP) =>
         { type:, bits:, operation: }
-      type = { 'f' => :float, 'i' => :integer, 'v' => :vector }.fetch(type)
+      type = { 'f' => :float, 'i' => :integer }.fetch(type)
       bits = bits.to_i(10)
 
       case operation
@@ -756,8 +752,6 @@ def parse_numeric_instruction
             parse_integer(bits:)
           in :float
             parse_float(bits:)
-          in :vector
-            parse_vector(bits:)
           end
 
         Const.new(type:, bits:, number:)
@@ -1093,14 +1087,6 @@ def parse_float(bits:)
       Float.parse(read).encode(format:)
     end
 
-    def parse_vector(bits:)
-      raise unless bits == 128
-      read => 'i64x2'
-      read => '0'
-      read => '0'
-      0
-    end
-
     def parse_string
       read => string
       encoding = string.encoding