docs: remove reference to src/tools/thread

This directory and the ability to build the thread test independently
were removed in commit 8a2121185b.

Reported-by: [email protected]
Discussion: https://postgr.es/m/160379609706.24746.7506163279454026608@wrigleys.postgresql.org

Backpatch-through: 9.5

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index de60281fcb496a20b4adc12d6795e9adbd96b519..9ce32fb39b54ab6746a628cd9a7801ed997bf991 100644 (file)
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -8052,14 +8052,6 @@ int PQisthreadsafe();
    libpq source code for a way to do cooperative
    locking between libpq and your application.
   
-
-  
-   If you experience problems with threaded applications, run the program
-   in src/tools/thread to see if your platform has
-   thread-unsafe functions.  This program is run by
-   configure, but for binary distributions your
-   library might not match the library used to build the binaries.
-