Correct enumerator name for kilopascal units in docs

The library declares an enum of the unit types supported for configuration of the return value of the `readPressure`
function. The names of the enumerators are documented in the API docs.

Previously, the name of the enumerator for kilopascal units was misspelled in the documentation.

Author: per1234

docs/api.md

@@ -84,7 +84,7 @@ BARO.readPressure(units)
 
 #### Parameters
 
-* _units_: `PSI`  to read the pressure in PSI (pounds per square inch), `MILLIBAR` to read the pressure in millibars and `KILOPASCALS` to read the pressure in kilopascals. If unit parameter is not provided, default is kilopascals   .
+* _units_: `PSI`  to read the pressure in PSI (pounds per square inch), `MILLIBAR` to read the pressure in millibars and `KILOPASCAL` to read the pressure in kilopascals. If unit parameter is not provided, default is kilopascals   .
 
 #### Returns
 
@@ -103,4 +103,4 @@ Serial.println(" kPa");
 #### See also
 
 * [begin()](#begin)
-* [end()](#end)
+* [end()](#end)