Bump Travis Xcode version to fix build error

Apparently they moved the location of libxml headers in the sdk? idfk

.travis.yml

@@ -1,35 +1,35 @@
 jobs:
-    include:
-        - &linux
-          language: c
-          os: linux
-          dist: bionic
-          addons:
-              apt:
-                  packages:
-                      - ninja-build
-          install:
-              - source ~/virtualenv/python3.6/bin/activate
-              - pip install meson
-          script:
-              - meson build $MESON_OPTS
-              - ninja -C build $NINJA_TARGET
-          env:
-              - MESON_OPTS=-Dengine=jit
-              - NINJA_TARGET=test
-          compiler: gcc
-        - <<: *linux
-          compiler: clang
-        - language: objective-c
-          os: osx
-          osx_image: xcode11
-          install:
-              - pip3 install meson
-          addons:
-              homebrew:
-                  packages:
-                      - ninja
-                      - llvm
-                  update: true
-          script:
-              - xcodebuild -project iSH.xcodeproj -scheme iSH -sdk iphoneos CODE_SIGNING_ALLOWED=NO
+  include:
+    - &linux
+      language: c
+      os: linux
+      dist: bionic
+      addons:
+        apt:
+            packages:
+                - ninja-build
+      install:
+        - source ~/virtualenv/python3.6/bin/activate
+        - pip install meson
+      script:
+        - meson build $MESON_OPTS
+        - ninja -C build $NINJA_TARGET
+      env:
+        - MESON_OPTS=-Dengine=jit
+        - NINJA_TARGET=test
+      compiler: gcc
+    - <<: *linux
+      compiler: clang
+    - language: objective-c
+      os: osx
+      osx_image: xcode11.5
+      install:
+        - pip3 install meson
+      addons:
+        homebrew:
+          packages:
+            - ninja
+            - llvm
+          update: true
+      script:
+        - xcodebuild -project iSH.xcodeproj -scheme iSH -sdk iphoneos CODE_SIGNING_ALLOWED=NO