DOC: add a missing space in the documentation for bc_http_major

add a missing space between sample fetch name and colon, and make
haproxy-dconv happier.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 5b6ab44..5a5e888 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -14396,7 +14396,7 @@
 tracked key will be looked up into this alternate table instead of the table
 currently being tracked.
 
-bc_http_major: integer
+bc_http_major : integer
   Returns the backend connection's HTTP major version encoding, which may be 1
   for HTTP/0.9 to HTTP/1.1 or 2 for HTTP/2. Note, this is based on the on-wire
   encoding and not the version present in the request header.