Previously this was hard coded to "0.1". The SCIP protocol allows this
to be an arbitrary string:
```
message ToolInfo {
// Name of the indexer that produced this index.
string name = 1;
// Version of the indexer that produced this index.
string version = 2;
// Command-line arguments that were used to invoke this indexer.
repeated string arguments = 3;
}
```
so use the same string reported by `rust-analyzer --version`.
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