use to uninterpreted integers in value definition text format

Uninterpreted integers can be written as either signed or unsigned and
therefore elliminate the need for distinction between the two rules

Signed-off-by: Roman Volosatovs <[email protected]>

Author: rvolosatovs

design/mvp/Explainer.md

@@ -1371,8 +1371,7 @@ Components may define values in the value index space using following syntax:
 ```ebnf
 value    ::= (value <id>? <valtype> <val>)
 val      ::= false | true
-           | <core:u64>
-           | <core:s64>
+           | <core:i64>
            | <f64canon>
            | nan
            | '<core:stringchar>'
@@ -2095,7 +2094,7 @@ and will be added over the coming months to complete the MVP proposal:
 [Index Space]: https://webassembly.github.io/spec/core/syntax/modules.html#indices
 [Abbreviations]: https://webassembly.github.io/spec/core/text/conventions.html#abbreviations
 
-[`core:i64`]: https://webassembly.github.io/spec/core/syntax/values.html#integers
+[`core:i64`]: https://webassembly.github.io/spec/core/text/values.html#text-int
 [`core:f64`]: https://webassembly.github.io/spec/core/syntax/values.html#floating-point
 [`core:char`]: https://webassembly.github.io/spec/core/syntax/values.html#syntax-name
 [`core:name`]: https://webassembly.github.io/spec/core/syntax/values.html#syntax-name