Travis-ci: Remove LDC 1.14 and 1.9.0

They have been consistently failing on the CI for months,
and there doesn't seem to be any interest in fixing it,
however they do block new PRs.

.travis.yml

@@ -14,8 +14,6 @@ d:
   - ldc-1.17.0
   - ldc-1.16.0
   - ldc-1.15.0
-  - ldc-1.14.0
-  - ldc-1.9.0
   - dmd-2.087.1
   - dmd-2.086.1
   - dmd-2.085.1
@@ -45,10 +43,6 @@ matrix:
         os: osx
       - d: ldc-1.15.0
         os: osx
-      - d: ldc-1.14.0
-        os: osx
-      - d: ldc-1.9.0
-        os: osx
   include:
     - d: dmd
       env: CONFIG='select' DUB_FLAGS='--build unittest-cov --build-mode=singleFile'