btrfs-progs: docs: add 6.14 kernel development statistics

[ci skip]

Signed-off-by: David Sterba <dsterba@suse.com>

Author: kdave

Documentation/Contributors.rst

@@ -58,6 +58,7 @@ Statistics for 6.x series
     "6.11", "18", "111848", "163484", "188", "+5776 -4043"
     "6.12", "20", "111881", "163548", "148", "+1868 -1804"
     "6.13", "25", "112756", "164722", "156", "+2780 -1579"
+    "6.14", "20", "114592", "167178", "147", "+3847 -1391"
 
 
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