installer checklist: suggest to run the script

To verify that Git for Windows installer works as intended, there is a
"pre-flight check list" in `checklist.txt`.

A few of the steps listed in that file have been performed manually with
every Git for Windows release and pre-release for years, until I got
tired of doing them manually (and I missed a few every once in a while),
which is when I started putting as much as I could into the
`run-checklist.sh` script.

Instead of duplicating the information in `checklist.txt` that is
already contained in the script, let `checklist.txt` suggest to run the
script instead.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

installer/checklist.txt

@@ -8,11 +8,8 @@ After building new installers, check that
 	- `gitk` runs and shows the history
 	- `git gui` runs and does not complain about a missing repository
 	- `git help git` opens the page and it has no verbatim `linkgit:`
-	- `curl --version` lists `IPv6` in the last line
-	- verify that `git -c http.sslbackend=schannel2 ls-remote
-	  https://github.com/dscho/images` errors out, and that it works with
-	  schannel and openssl
-	- verify that `git ls-remote` works with a VSTS SSH URL
+	- `run-checklist.sh` passes (performs a couple automated tests related
+	  to cURL, the Git version, etc)
 - Git CMD
 	- starts
 	- `git log` in a repository is colorful and stops after the first page