[libc][doc] Update implementation status of tanhf.

GitOrigin-RevId: 69cc240534ce64d89a9c4204f1a04ae3b65a422b
diff --git a/docs/math.rst b/docs/math.rst
index f5f6a6e..4445c1a 100644
--- a/docs/math.rst
+++ b/docs/math.rst
@@ -144,7 +144,7 @@
 sinh           |check|
 sqrt           |check|          |check|         |check|
 tan
-tanh
+tanh           |check|
 tgamma
 ============== ================ =============== ======================
 
@@ -169,6 +169,7 @@
 sincos         0.776 ULPs       large
 sinh           |check|
 sqrt           |check|          |check|         |check|
+tanh           |check|
 ============== ================ =============== ======================
 
 Legends:
@@ -233,6 +234,8 @@
 +--------------+-----------+-------------------+-----------+-------------------+-------------------------------------+------------+-------------------------+--------------+---------------+
 | sinhf        |        23 |                64 |        73 |               141 | :math:`[-10, 10]`                   | Ryzen 1700 | Ubuntu 20.04 LTS x86_64 | Clang 12.0.0 | FMA           |
 +--------------+-----------+-------------------+-----------+-------------------+-------------------------------------+------------+-------------------------+--------------+---------------+
+| tanhf        |        25 |                59 |        95 |               125 | :math:`[-10, 10]`                   | Ryzen 1700 | Ubuntu 20.04 LTS x86_64 | Clang 12.0.0 | FMA           |
++--------------+-----------+-------------------+-----------+-------------------+-------------------------------------+------------+-------------------------+--------------+---------------+
 
 References
 ==========