Update linalg user guide.

Author: hunghaoti

docs/source/guide/linalg.rst

@@ -1,7 +1,7 @@
 Linear algebra
 ===============
 
-Currently, Cytnx supports the following linear algebra functions. See A for further documentation.
+Currently, Cytnx supports the following linear algebra functions. See the :cytnx_linalg:`API documentation<>`  for more details.
 
 +-----------------------------------------------------------------------+---------+-----+------+-------------+----+----------------+
 |   func                                                                | Inplace | CPU | GPU  | Called by Tn| Tn | CyTn (xlinalg) |