perf build: Remove explicit reference to python 2.x devel files

If the libpython feature test (tools/build/feature/test-libpython.c)
fails, then the python-devel is missing, it doesn't mattere if it is for
python2 or 3, remove that explicit 2.x reference.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Makefile.config

@@ -886,7 +886,7 @@ else
     else
 
       ifneq ($(feature-libpython), 1)
-        $(call disable-python,No 'Python.h' (for Python 2.x support) was found: disables Python support - please install python-devel/python-dev)
+        $(call disable-python,No 'Python.h' was found: disables Python support - please install python-devel/python-dev)
       else
          LDFLAGS += $(PYTHON_EMBED_LDFLAGS)
          EXTLIBS += $(PYTHON_EMBED_LIBADD)