Revert "travis-ci: use travis_retry to reduce number of problems with flacky tests"

That was a bad idea, because all this patch did is just uses extra CPU
time on travis-ci workers and eventually fail the build anyway.

It also increases time of executing one matrix entry (x3).

This reverts commit 7004ee8e869faabe3a284fb3d7eb859fb50ef90c.

.travis.yml

@@ -78,7 +78,7 @@ script:
       ./autogen.sh &&
       ./configure $EVENT_CONFIGURE_OPTIONS &&
       make &&
-      travis_retry travis_wait $TIMEOUT make -j $JOBS verify;
+      travis_wait $TIMEOUT make -j $JOBS verify;
     fi
   - if [ "$EVENT_BUILD_METHOD" = "cmake" ]; then
       export
@@ -88,7 +88,7 @@ script:
       mkdir build &&
       cd build &&
       cmake .. $EVENT_CMAKE_OPTIONS &&
-      travis_retry travis_wait $TIMEOUT
+      travis_wait $TIMEOUT
       cmake --build . --target verify;
     fi