doc: posix: mark confstr() as supported

Mark confstr() as supported in POSIX Option Groups.

Signed-off-by: Christopher Friedt <[email protected]>

Author: cfriedt

doc/services/portability/posix/option_groups/index.rst

@@ -163,7 +163,7 @@ process applications.
    :header: API, Supported
    :widths: 50,10
 
-    confstr(),
+    confstr(),yes
     environ,yes
     errno,yes
     getenv(),yes