Fix double-space in exception message (GH-29955)

(cherry picked from commit c602c1be439e295fed9ebab47e895ef1d9df28be)

Co-authored-by: Ned Batchelder <ned@nedbatchelder.com>
diff --git a/Lib/statistics.py b/Lib/statistics.py
index cfcc456..f662453 100644
--- a/Lib/statistics.py
+++ b/Lib/statistics.py
@@ -374,7 +374,7 @@ def geometric_mean(data):
         return exp(fmean(map(log, data)))
     except ValueError:
         raise StatisticsError('geometric mean requires a non-empty dataset '
-                              ' containing positive numbers') from None
+                              'containing positive numbers') from None
 
 
 def harmonic_mean(data, weights=None):