Update latest version in doc (#2508)

docs/en_US/Tuner/PBTTuner.md

@@ -46,7 +46,3 @@ tuner:
     all_checkpoint_dir: /the/path/to/store/checkpoints
     population_size: 10
 ```
-
-### Limitation
-
-Importing data has not been supported yet.
\ No newline at end of file

docs/en_US/Tutorial/InstallationLinux.md

@@ -19,7 +19,7 @@ Installation on Linux and macOS follow the same instructions, given below.
   Prerequisites: `python 64-bit >=3.5`, `git`, `wget`
 
   ```bash
-  git clone -b v1.5 https://github.com/Microsoft/nni.git
+  git clone -b v1.6 https://github.com/Microsoft/nni.git
   cd nni
   ./install.sh
   ```
@@ -35,7 +35,7 @@ The following example is built on TensorFlow 1.x. Make sure **TensorFlow 1.x is
 * Download the examples via cloning the source code.
 
   ```bash
-  git clone -b v1.5 https://github.com/Microsoft/nni.git
+  git clone -b v1.6 https://github.com/Microsoft/nni.git
   ```
 
 * Run the MNIST example.

docs/en_US/Tutorial/InstallationWin.md

@@ -29,7 +29,7 @@ If you want to contribute to NNI, refer to [setup development environment](Setup
 * From source code
 
     ```bat
-    git clone -b v1.5 https://github.com/Microsoft/nni.git
+    git clone -b v1.6 https://github.com/Microsoft/nni.git
     cd nni
     powershell -ExecutionPolicy Bypass -file install.ps1
     ```
@@ -41,7 +41,7 @@ The following example is built on TensorFlow 1.x. Make sure **TensorFlow 1.x is
 * Clone examples within source code.
 
     ```bat
-    git clone -b v1.5 https://github.com/Microsoft/nni.git
+    git clone -b v1.6 https://github.com/Microsoft/nni.git
     ```
 
 * Run the MNIST example.

docs/en_US/conf.py

@@ -28,7 +28,7 @@ author = 'Microsoft'
 # The short X.Y version
 version = ''
 # The full version, including alpha/beta/rc tags
-release = 'v1.5'
+release = 'v1.6'
 
 # -- General configuration ---------------------------------------------------