Correct minor typo in exception raised when exemplar labels too long (#773)

Signed-off-by: Rob Skillington <[email protected]>

Author: robskillington

prometheus_client/openmetrics/parser.py

@@ -354,7 +354,7 @@ def _parse_remaining_text(text):
     if exemplar_labels is not None:
         exemplar_length = sum(len(k) + len(v) for k, v in exemplar_labels.items())
         if exemplar_length > 128:
-            raise ValueError("Exmplar labels are too long: " + text)
+            raise ValueError("Exemplar labels are too long: " + text)
         exemplar = Exemplar(
             exemplar_labels,
             _parse_value(exemplar_value),