docs: fix wrong expression in type precision description (#607)

In type classes documentation, precision range of type
`PRECISIONTIMESTAMP` and `PRECISIONTIMESTAMPTZ` are wrong:

```
0 >= P <= 9
```

and it should be: 

```
0 <= P <= 9
```

site/docs/types/type_classes.md

@@ -41,8 +41,8 @@ Compound type classes are type classes that need to be configured by means of a
 | NSTRUCT<N:T1,...,N:Tn>  | **Pseudo-type**: A struct that maps unique names to value types. Each name is a UTF-8-encoded string. Each value can have a distinct type. Note that NSTRUCT is actually a pseudo-type, because Substrait's core type system is based entirely on ordinal positions, not named fields. Nonetheless, when working with systems outside Substrait, names are important. | n/a
 | LIST<T>                 | A list of values of type T. The list can be between [0..2,147,483,647] values in length.                                                                                                                                                                                                                                                                              | `repeated Literal`, all types matching T
 | MAP<K, V>               | An unordered list of type K keys with type V values. Keys may be repeated. While the key type could be nullable, keys may not be null.                                                                                                                                                                                                                                | `repeated KeyValue` (in turn two `Literal`s), all key types matching K and all value types matching V
-| PRECISIONTIMESTAMP&lt;P&gt;   | A timestamp with fractional second precision (P, number of digits) 0 >= P <= 9. Does not include timezone information and can thus not be unambiguously mapped to a moment on the timeline without context. Similar to naive datetime in Python.                                                                                                                      | `uint64` microseconds or nanoseconds since 1970-01-01 00:00:00.000000000 (in an unspecified timezone)
-| PRECISIONTIMESTAMPTZ&lt;P&gt; | A timezone-aware timestamp, with fractional second precision (P, number of digits) 0 >= P <= 9. Similar to aware datetime in Python.                                                                                                                                                                                                                                  | `uint64` microseconds or nanoseconds since 1970-01-01 00:00:00.000000000 UTC
+| PRECISIONTIMESTAMP&lt;P&gt;   | A timestamp with fractional second precision (P, number of digits) 0 <= P <= 9. Does not include timezone information and can thus not be unambiguously mapped to a moment on the timeline without context. Similar to naive datetime in Python.                                                                                                                      | `uint64` microseconds or nanoseconds since 1970-01-01 00:00:00.000000000 (in an unspecified timezone)
+| PRECISIONTIMESTAMPTZ&lt;P&gt; | A timezone-aware timestamp, with fractional second precision (P, number of digits) 0 <= P <= 9. Similar to aware datetime in Python.                                                                                                                                                                                                                                  | `uint64` microseconds or nanoseconds since 1970-01-01 00:00:00.000000000 UTC
 
 ## User-Defined Types