doc: column: fix blank lines around block delimiters

227c4f33a0 (doc: add a blank line around block delimiters,
2025-03-09) added blank lines around block delimiters as a
defensive measure.  For each block you had to mind the con-
text (like the commit says):

• Top-level: just add blank lines
• Block: use list continuation (+)

But list continuation was used here at the top level, which
results in literal `+` in the output formats.

Acked-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-column.adoc

@@ -50,7 +50,7 @@ EXAMPLES
 --------
 
 Format data by columns:
-+
+
 ------------
 $ seq 1 24 | git column --mode=column --padding=5
 1      4      7      10     13     16     19     22
@@ -59,7 +59,7 @@ $ seq 1 24 | git column --mode=column --padding=5
 ------------
 
 Format data by rows:
-+
+
 ------------
 $ seq 1 21 | git column --mode=row --padding=5
 1      2      3      4      5      6      7
@@ -68,7 +68,7 @@ $ seq 1 21 | git column --mode=row --padding=5
 ------------
 
 List some tags in a table with unequal column widths:
-+
+
 ------------
 $ git tag --list 'v2.4.*' --column=row,dense
 v2.4.0  v2.4.0-rc0  v2.4.0-rc1  v2.4.0-rc2  v2.4.0-rc3