MDL-57450 enviroment: remove tls library check

Unfortunately it has come to light that the version sniffing is just not
reliable at all, operating system vendors backport security patches to
older versions - so in many cases we reporting a problem which is not a
problem. False positives and the solution to self-compile or something
like php will be causing more harm than good.

admin/environment.xml

@@ -1868,11 +1868,6 @@
           <ON_CHECK message="unoconvwarning" />
         </FEEDBACK>
       </CUSTOM_CHECK>
-      <CUSTOM_CHECK file="lib/upgradelib.php" function="check_tls_libraries" level="optional">
-        <FEEDBACK>
-          <ON_CHECK message="tlswarning" />
-        </FEEDBACK>
-      </CUSTOM_CHECK>
       <CUSTOM_CHECK file="lib/upgradelib.php" function="check_libcurl_version" level="optional">
         <FEEDBACK>
           <ON_CHECK message="libcurlwarning" />

lib/upgradelib.php

@@ -2325,7 +2325,7 @@ function check_unoconv_version(environment_results $result) {
 }
 
 /**
- * Checks for up-to-date TLS libraries.
+ * Checks for up-to-date TLS libraries. NOTE: this is not currently used, see MDL-57262.
  *
  * @param environment_results $result object to update, if relevant.
  * @return environment_results|null updated results or null if unoconv path is not executable.