Fix Phalcon sample app link for PHP Buildpack docs
Fix Phalcon sample app link for PHP Buildpack docs

[#128896127]

Signed-off-by: James Wen <3b2f4c88287a5fcd7db73a67dd1ab82807db04ee@columbia.edu>

cloudfoundry/docs-buildpacks,TimGerlach/docs-buildpacks