fixes a new validation failure in a UniformId test (#3301)
A recent spirv-val change requires that OpDecorateId IDs are
well-ordered, which means that the decoration operand ID cannot be the
same as the decoration target ID. See:
https://github.com/KhronosGroup/SPIRV-Tools/pull/6227
This leads to the failure:
```
error: line 6: Parameter <ID> '2[%uint_0]' must appear earlier in the binary than the target
OpDecorateId %uint_0 UniformId %uint_0
```
The fix is to use a different ID for the decoration operand and the
decoration target.
Original commit:
https://github.com/KhronosGroup/SPIRV-LLVM-Translator/commit/fc5873ee760c333
