ci: Use env to be coherent on bash shebang

As per previous commit we're figuring out the bash location on shebang
using env, let's do it everywhere for coherency, even if in CI fedora
may not yet have issues about this.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4288>

.gitlab-ci/download-coverity-tarball.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # We need a coverity token to fetch the tarball
 if [ -x $COVERITY_TOKEN ]

.gitlab-ci/install-common-dependencies.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -e
 

.gitlab-ci/install-gnomeos-sysext-dependencies.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -e
 

.gitlab-ci/install-meson-project.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -e
 

.gitlab-ci/simple-junit-report.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 OUTFILE=$1
 NAME=$2
 MESSAGE=$3