[ci] reduced number of commits cloned to CI environments (#2495)

* reduced number of commits cloned to CI environments

* changed clone depth for CI to 5 commits

.appveyor.yml

@@ -10,7 +10,7 @@ environment:
     - COMPILER: MSVC
     - COMPILER: MINGW
 
-clone_depth: 50
+clone_depth: 5
 
 install:
   - git submodule update --init --recursive  # get `compute` folder

.travis.yml

@@ -2,6 +2,7 @@ language: cpp
 
 git:
   submodules: true
+  depth: 5
 
 os:
   - linux