build(cmake): upgrade catch2 to 2.13.9

[leogr]

What type of PR is this?

/kind bug

Any specific area of the project related to this PR?
/area build

What this PR does / why we need it:

Upgrading catch2 addresses the problem reported in the following log:

In file included from /usr/include/signal.h:328,
                 from /home/leogr/code/github.com/falcosecurity/falco/build/catch2-prefix/include/catch.hpp:8007,
                 from /home/leogr/code/github.com/falcosecurity/falco/tests/test_base.cpp:18:
/home/leogr/code/github.com/falcosecurity/falco/build/catch2-prefix/include/catch.hpp:10791:58: error: call to non-'constexpr' function 'long int sysconf(int)'
10791 |     static constexpr std::size_t sigStackSize = 32768 >= MINSIGSTKSZ ? 32768 : MINSIGSTKSZ;
      |                                                          ^~~~~~~~~~~
In file included from /usr/include/bits/sigstksz.h:24,
                 from /usr/include/signal.h:328,
                 from /home/leogr/code/github.com/falcosecurity/falco/build/catch2-prefix/include/catch.hpp:8007,
                 from /home/leogr/code/github.com/falcosecurity/falco/tests/test_base.cpp:18:
/usr/include/unistd.h:640:17: note: 'long int sysconf(int)' declared here
  640 | extern long int sysconf (int __name) __THROW;
      |                 ^~~~~~~
In file included from /home/leogr/code/github.com/falcosecurity/falco/tests/test_base.cpp:18:
/home/leogr/code/github.com/falcosecurity/falco/build/catch2-prefix/include/catch.hpp:10850:45: error: size of array 'altStackMem' is not an integral constant-expression
10850 |     char FatalConditionHandler::altStackMem[sigStackSize] = {};
      |                                             ^~~~~~~~~~~~

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

/milestone 0.32.0

Does this PR introduce a user-facing change?:

build(cmake): upgrade catch2 to 2.13.9

[jasondellaluce]

/approve

[poiana]

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