[ci skip] Remove make install step from README

The `make install` step touches files outside of the source directory
and might cause confusions with people. It should be mentioned in more
details elsewhere in the installation chapter instead and how to
override it.

README.md

@@ -41,7 +41,6 @@ On \*nix systems:
     ./configure
     make
     make test
-    sudo make install
 
 See `./configure -h` and `make -h` for configuration options. For example, the
 `-j` option allows parallel execution of the build recipes where `N` is the