doc: fix xref link from api docs to manual pages

They are one-level above, so refer them as linkgit:../git-foo[n] with "../"

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: gitster

Documentation/technical/api-config.txt

@@ -2,7 +2,7 @@ config API
 ==========
 
 The config API gives callers a way to access git configuration files
-(and files which have the same syntax). See linkgit:git-config[1] for a
+(and files which have the same syntax). See linkgit:../git-config[1] for a
 discussion of the config file syntax.
 
 General Usage

Documentation/technical/api-merge.txt

@@ -36,7 +36,7 @@ the operation of a low-level (single file) merge.  Some options:
 	ancestors in a recursive merge.
 	If a helper program is specified by the
 	`[merge "<driver>"] recursive` configuration, it will
-	be used (see linkgit:gitattributes[5]).
+	be used (see linkgit:../gitattributes[5]).
 
 `variant`::
 	Resolve local conflicts automatically in favor