Stop testing libclang 4.0

Author: kulp

.travis.yml

@@ -17,13 +17,6 @@ env:
     - LLVM_VERSION="9.0" BINDGEN_JOB="msrv"
 
     # General matrix.
-    - LLVM_VERSION="4.0" BINDGEN_JOB="test"         BINDGEN_PROFILE=
-    - LLVM_VERSION="4.0" BINDGEN_JOB="test"         BINDGEN_PROFILE="--release"
-    - LLVM_VERSION="4.0" BINDGEN_JOB="integration"  BINDGEN_PROFILE=
-    - LLVM_VERSION="4.0" BINDGEN_JOB="integration"  BINDGEN_PROFILE="--release"
-    - LLVM_VERSION="4.0" BINDGEN_JOB="test"         BINDGEN_PROFILE=            BINDGEN_NO_DEFAULT_FEATURES="1" BINDGEN_FEATURES="runtime"
-    - LLVM_VERSION="4.0" BINDGEN_JOB="test"         BINDGEN_PROFILE="--release" BINDGEN_NO_DEFAULT_FEATURES="1" BINDGEN_FEATURES="runtime"
-
     - LLVM_VERSION="5.0" BINDGEN_JOB="test"         BINDGEN_PROFILE=
     - LLVM_VERSION="5.0" BINDGEN_JOB="test"         BINDGEN_PROFILE="--release"
     - LLVM_VERSION="5.0" BINDGEN_JOB="integration"  BINDGEN_PROFILE=