build: drop libunwind build dependency from rpm/deb

The dependency is redundant, because the library is now bundled into
tarantool (see PR #6877).

There is a practical reason to remove it: this way we'll verify that
presence of system libunwind headers is not necessary to build
tarantool. In other words, we'll verify that #8025 will not appear
again.

Follows up #8025
Follows up #6877
Part of #6998

NO_DOC=No user visible changes, just some validation for a build fix.
NO_TEST=See NO_DOC.
NO_CHANGELOG=See a changelog entry in the previous commit.

debian/control

@@ -22,7 +22,6 @@ Build-Depends: cdbs (>= 0.4.100), debhelper (>= 9), dpkg-dev (>= 1.16.1~),
  libreadline-dev,
  libncurses5-dev,
  libssl-dev,
- libunwind-dev | libunwind8-dev | libunwind7-dev,
  libicu-dev,
 # libcurl build dependencies
  zlib1g-dev,

rpm/tarantool.spec

@@ -75,7 +75,6 @@ Requires(preun): initscripts
 %undefine __cc
 
 %if %{with backtrace}
-BuildRequires: libunwind-devel
 #
 # Disable stripping of /usr/bin/tarantool to allow the debug symbols
 # in runtime. Tarantool uses the debug symbols to display fiber's stack