[FIRRTL][enumcreate] textual IR prints attributes but can't read back

Nobody has claimed this yet.

Consider this input:
```
firrtl.circuit "MatchTest" {
firrtl.module @MatchTest(in %i: !firrtl.enum, None: uint<0>>) attributes {convention = #firrtl} {
%c0_ui8 = firrtl.constant 0 : !firrtl.const.uint<8>
%0 = firrtl.enumcreate Some(%c0_ui8) : (!firrtl.const.uint<8>) -> !firrtl.enum, None: uint<0>>
%some = firrtl.node interesting_name %0 : !firrtl.enum, None: uint<0>>
%c0_ui0 = firrtl.constant 0 : !firrtl.const.uint<0>
%1 = firrtl.enumcreate None(%c0_ui0) : (!firrtl.const.uint<0>) -> !firrtl.enum, None: uint<0>>
%none = firrtl.node interesting_name %1 : !firrtl.enum, None: uint<0>>
}
}
```

Fed through this pipeline:
```
circt-opt --no-implicit-module -p 'firrtl.circuit(firrtl.module(firrtl-lower-matches,firrtl-expand-whens,firrtl-drop-names,canonicalize))' match-test-name.mlir
```

Produces:
```
firrtl.circuit "MatchTest" {
firrtl.module @MatchTest(in %i: !firrtl.enum, None: uint<0>>) attributes {convention = #firrtl} {
%c0_ui0 = firrtl.constant 0 : !firrtl.const.uint<0>
%c0_ui8 = firrtl.constant 0 : !firrtl.const.uint<8>
%0 = firrtl.enumcreate Some(%c0_ui8) attributes {name = "some"} : (!firrtl.const.uint<8>) -> !firrtl.enum, None: uint<0>>
%1 = firrtl.enumcreate None(%c0_ui0) attributes {name = "none"} : (!firrtl.const.uint<0>) -> !firrtl.enum, None: uint<0>>
}
}
```

(names from nodes to go their inputs, cc #7064, I think so that we give nicer names should these becomes name-able things, but regardless)

This IR can't be parsed, failure at `attributes`:

```
:5:41: error: expected ':'
%0 = firrtl.enumcreate Some(%c0_ui8) attributes {name = "some"} : (!firrtl.const.uint<8>) -> !firrtl.enum, None: uint<0>>
```

Reproduce the issue with the provided FIRRTL input and circt-opt pipeline, then trace the FIRRTL enumcreate textual parser and printer handling. The fix is done when the printed IR containing enumcreate attributes can be parsed successfully without the reported error.

Written by the indexing model from the issue text.