readme: fix repository url

The unauthenticated git protocol on port 9418 is no longer supported.

NO_DOC=doc
NO_TEST=doc
NO_CHANGELOG=doc

(cherry picked from commit 12cf9980)

README.FreeBSD

@@ -8,7 +8,7 @@ pkg install git cmake gmake readline icu libiconv
 2. Download & build tarantool source code:
 -------------
 
-git clone git://github.com/tarantool/tarantool.git
+git clone https://github.com/tarantool/tarantool.git
 
 cd tarantool
 mkdir build && cd build

README.OpenBSD

@@ -7,7 +7,7 @@ pkg_add git m4 curl cmake gmake
 2. Download & build tarantool source code
 -----------------------------------------
 
-git clone git://github.com/tarantool/tarantool.git
+git clone https://github.com/tarantool/tarantool.git
 
 cd tarantool
 git submodule update --init --recursive