fix(nspr): drop runtests.pl so nspr-dev does not need perl

[JanZachmann]

Summary

New nspr bbappend that deletes ${libdir}/nspr/tests/runtests.pl for target builds.

Reason

#690 broke the build. RDEPENDS:nspr-dev:remove = "perl" takes perl out of the build graph, but nspr-dev still ships a perl script, so the file-rdeps QA check fails:

ERROR: nspr-4.38.2-r0 do_package_qa: QA Issue: /usr/lib/nspr/tests/runtests.pl contained in package nspr-dev requires /usr/bin/perl, but no providers found in RDEPENDS:nspr-dev? [file-rdeps]
ERROR: nspr-4.38.2-r0 do_package_qa: Fatal QA errors were found, failing task.

The recipe installs that script itself (install -m 0755 ${S}/pr/tests/runtests.pl ${D}${libdir}/nspr/tests) and packages it through the ${libdir}/nspr/tests/* glob in FILES:${PN}-dev. It only drives the nspr test binaries, which no image runs, and the recipe already deletes compile-et.pl from ${bindir} for exactly the same reason. Deleting this one file is therefore the honest fix; the alternative, INSANE_SKIP:nspr-dev += "file-rdeps", would only silence a check that is telling the truth.

This is a build-machine-independent failure: it is nspr:do_package_qa, so it hits every build whose graph contains nspr. From the same trigger (wrynose/dev/gateway-devel, build 6):

• rpi4-omnect-lab failed at 13:44 - the first build to reach that task
• genericx86-64 hit the identical error while still running
• dehndetect passed: nspr does not appear once in its build log, so that image does not pull it in
• tauril2 build 6 errored for an unrelated reason (no nspr in its log); 6.1 is running
• rpi4 was still before that task at the time of writing

If CI still fails on nspr after this, the fallback is to revert the RDEPENDS:nspr-dev:remove line from #690 and accept perl in the build and the SBOM again.