Allow labelvalues and labelkwargs to be Any type

We will cast all labelvalues to be strings so we should not force a user
to cast to a string before passing the label.

Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>

prometheus_client/metrics.py

@@ -133,7 +133,7 @@ def __init__(self: T,
             if registry:
                 registry.register(self)
 
-    def labels(self: T, *labelvalues: str, **labelkwargs: str) -> T:
+    def labels(self: T, *labelvalues: Any, **labelkwargs: Any) -> T:
         """Return the child for the given labelset.
 
         All metrics can have labels, allowing grouping of related time series.