[format.mod] Documentation misses a % sign

https://blitzmax.org/docs/en/api/text/text.format/
contains the sample:
```
Local formatter:TFormatter = TFormatter.Create("VAT = <i>2.1f</i>%%")
```
Yet it must be 
```
'                                                       -.-
Local formatter:TFormatter = TFormatter.Create("VAT = <i>%2.1f</i>%%")
```