sagemathgh-36726: CI Linux: Replace use of pkill

Follow-up after:
- sagemath#36670

This is working well, for example see https://github.com/mkoeppe/sage/ac
tions/runs/6874334523/job/18695809308#step:11:5345, making it possible
to obtain the image of the hanging build - https://github.com/mkoeppe/sa
ge/actions/runs/6874334523/job/18695809308#step:15:25

However, `pkill` is not present on many of our `-minimal` configurations
(which test our documented minimal build prerequisites). For example
`debian-sid-minimal`, as seen in https://github.com/mkoeppe/sage/actions
/runs/6874334523/job/18695811066#step:11:2262, rendering the mechanism
ineffective there. (Neither are `ps` and `killall`.)

Examples:
- `docker run -it ghcr.io/sagemath/sage/sage-debian-bookworm-minimal-
with-system-packages:dev bash -c "command -v pkill" `
- `docker run -it ghcr.io/sagemath/sage/sage-fedora-38-minimal-with-
system-packages:dev bash -c "command -v pkill"`
- whereas `docker run -it ghcr.io/sagemath/sage/sage-fedora-38-standard-
with-system-packages:dev bash -c "command -v pkill" ` -->
`/usr/bin/pkill`.

We replace `pkill` by more primitive means.

Test run (with timeout set to ~11 minutes for testing purposes): https:/
/github.com/mkoeppe/sage/actions/runs/6883232154/job/18723359505#step:15
:25

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URL: sagemath#36726
Reported by: Matthias Köppe
Reviewer(s): Kwankyu Lee, Nathan Dunfield, William Stein

build/pkgs/configure/checksums.ini

@@ -1,4 +1,4 @@
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build/pkgs/configure/package-version.txt

@@ -1 +1 @@
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