Revert "Avoid warning with Clang that doesn't have -Wunused-but-set-parameter"

This reverts commit d69bc9c939, which isn't needed
any more now that 01aa52b5e9 "Work around
-Werror,-Wunknown-pragmas" makes the whole pragma block conditional on

  __GNUC__ >= 7

(which Clang does not fulfill).

ucb/source/ucp/cmis/auth_provider.hxx

@@ -12,10 +12,8 @@
 #if defined __GNUC__ && __GNUC__ >= 7
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated"
-#ifndef __clang__
 #pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #endif
-#endif
 #include <libcmis/libcmis.hxx>
 #if defined __GNUC__ && __GNUC__ >= 7
 #pragma GCC diagnostic pop

ucb/source/ucp/cmis/certvalidation_handler.hxx

@@ -15,10 +15,8 @@
 #if defined __GNUC__ && __GNUC__ >= 7
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated"
-#ifndef __clang__
 #pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #endif
-#endif
 #include <libcmis/libcmis.hxx>
 #if defined __GNUC__ && __GNUC__ >= 7
 #pragma GCC diagnostic pop

ucb/source/ucp/cmis/cmis_content.hxx

@@ -27,10 +27,8 @@
 #if defined __GNUC__ && __GNUC__ >= 7
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated"
-#ifndef __clang__
 #pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #endif
-#endif
 #include <libcmis/libcmis.hxx>
 #if defined __GNUC__ && __GNUC__ >= 7
 #pragma GCC diagnostic pop

ucb/source/ucp/cmis/cmis_url.cxx

@@ -10,10 +10,8 @@
 #if defined __GNUC__ && __GNUC__ >= 7
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated"
-#ifndef __clang__
 #pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #endif
-#endif
 #include <libcmis/libcmis.hxx>
 #if defined __GNUC__ && __GNUC__ >= 7
 #pragma GCC diagnostic pop