tests: fix broken rm in gzip.exp

This amends commit 29da82d08 ("private-etc: kdiff3, gzip, gunzip, tar
etc", 2023-02-10).

This is causing CI to fail, as "index.html" has nothing to do with
gzip.exp[1]:

    ##[group]Run make test-sysutils
    make test-sysutils
    shell: /usr/bin/bash -e {0}
    env:
      SHELL: /bin/bash
    ##[endgroup]
    make -C test sysutils
    make[1]: Entering directory '/home/runner/work/firejail/firejail/test'
    cd sysutils && ./sysutils.sh 2>&1 | tee sysutils.log
    /usr/bin/gzip
    TESTING: gzip
    spawn /bin/bash
    rm index.html*
    runner@fv-az1391-790:~/work/firejail/firejail/test/sysutils$ rm index.html*
    rm: cannot remove 'index.html*': No such file or directory
    runner@fv-az1391-790:~/work/firejail/firejail/test/sysutils$
    <irejail gzip -c ../../mkdeb.sh | firejail gunzip -c
    TESTING ERROR 1

[1] https://github.com/netblue30/firejail/actions/runs/8739405468/job/23982517624:

1 files changed, 0 insertions, 3 deletions

diff --git a/test/sysutils/gzip.exp b/test/sysutils/gzip.exp
index 5492391e0..8d69087f8 100755
--- a/test/sysutils/gzip.exp
+++ b/test/sysutils/gzip.exp
@@ -7,9 +7,6 @@ set timeout 10
 spawn $env(SHELL)
 match_max 100000
 
-send -- "rm index.html*\r"
-after 500
-
 send -- "firejail gzip -c ../../mkdeb.sh | firejail gunzip -c\r"
 expect {
         timeout {puts "TESTING ERROR 1\n";exit}