[FAB-7988]Fix typo in fabric/docs/source/samples.rst

Fabric’s version is still 1.1.0-preview
in a note of fabric/docs/source/samples.rst.
This CR updates the version to 1.1.0-alpha.

Change-Id: I672ccde70a50e29fcce2330d6f9d35fa5fbea33d
Signed-off-by: Yuki Kondo <yuki.kondo@hal.hitachi.com>

Author: yuki-kon

docs/source/samples.rst

@@ -57,8 +57,8 @@ you will extract the platform-specific binaries:
 	  https://github.com/hyperledger/fabric/blob/master/scripts/bootstrap.sh
 
 .. note:: You can use the command above for any published version of Hyperledger
-          Fabric. Simply replace '1.1.0-preview' with the version identifier
-					of the version you wish to install.
+          Fabric. Simply replace '1.1.0-alpha' with the version identifier
+          of the version you wish to install.
 
 The command above downloads and executes a bash script
 that will download and extract all of the platform-specific binaries you