unbreak event tracer's app.src

[Mikael Pettersson]

lib/et/src/et.app.src lists a module (et_contents_viewer) for which
there is no source module, so it doesn't get built or installed.
This breaks tools like HiPE's big test suite that parse installed .app
files and expect to find a .beam file for every listed module.

Fixed by deleting the offending line. I also noticed a duplicated
line for the et_viewer module, and deleted that too.

--- otp-0211/lib/et/src/et.app.src.~1~	2010-02-11 15:14:03.000000000 +0100
+++ otp-0211/lib/et/src/et.app.src	2010-02-11 20:43:33.000000000 +0100
@@ -24,12 +24,10 @@
    [
     et,
     et_collector,
-    et_contents_viewer,
     et_gs_contents_viewer,
     et_gs_viewer,
     et_selector,
     et_viewer,
-    et_viewer,
     et_wx_contents_viewer,
     et_wx_viewer
    ]},