configure*: remove ultimately unused INSTALL and RANLIB check macros

[kmk3]

From the manual of GNU Autoconf (version 2.69):

-- Macro: AC_PROG_INSTALL
Set output variable 'INSTALL' to the name of a BSD-compatible
'install' program, if one is found in the current 'PATH'.
Otherwise, set 'INSTALL' to 'DIR/install-sh -c', checking the
directories specified to 'AC_CONFIG_AUX_DIR' (or its default
directories) to determine DIR (*note Output::). Also set the
variables 'INSTALL_PROGRAM' and 'INSTALL_SCRIPT' to '${INSTALL}'
and 'INSTALL_DATA' to '${INSTALL} -m 644'.

-- Macro: AC_PROG_RANLIB
Set output variable 'RANLIB' to 'ranlib' if 'ranlib' is found,
and otherwise to ':' (do nothing).

None of the aforementioned variables are used:

$ git grep -F -e '${INSTALL}' -e INSTALL_PROGRAM -e INSTALL_SCRIPT \
  -e INSTALL_DATA -e RANLIB
$

So remove the macros that define them.

Misc: The macros in question have been present on configure.ac since it
was created, on commit 1379851 ("Baseline firejail 0.9.28",
2015-08-08). And while the install command is called multiple times,
ranlib is not used anywhere (and it seems that it was never used):

$ git grep -E '^[[:blank:]]+install ' -- '*Makefile*' '*.mk*' |
  wc -l
32
$ git grep -F ranlib | wc -l
0
$ git log --pretty= --name-only -G'RANLIB|ranlib' \
  137985136..master | sort -u
README.md

Kind of relates to #4695.

[kmk3]

By the way, I'm working on other build-related improvements (involving the
makefiles).