Bump bat version in test environment

And fix the theme script because it broke.

With bat 0.25.0, the following command
bat --list-themes --color=never

... lists the default dark and light themes appending
" (default)" and " (default light)" to their names.

But `bat --theme=<THEME_NAME>` doesn't recognize names with that part
added in, so we have to remove it.

Author: victor-gp

tests/docker/bat-test.dockerfile

@@ -5,7 +5,7 @@
 
 FROM curlimages/curl:latest AS fetch-pkg
 LABEL keep=false
-ARG BAT_VERSION=0.24.0
+ARG BAT_VERSION=0.25.0
 RUN curl -LJ \
     https://github.com/sharkdp/bat/releases/download/v$BAT_VERSION/bat_${BAT_VERSION}_amd64.deb \
     --output /tmp/bat.deb

tests/docker/inner_theme_regression.sh

@@ -10,7 +10,10 @@ synthetic_src="source/theme/synthetic.txt"
 
 readarray -t themes <<< "$(bat --list-themes --color=never)"
 
-for theme in "${themes[@]}"; do
+for theme_ in "${themes[@]}"; do
+    # strip " (default)" and " (default light)" from theme name, because bat doesn't recognize that
+    theme="${theme_% \(default*\)}"
+
     $cmd_prefix --theme="$theme" $brief_src > "theme/brief-${theme}.txt"
 
     synthetic_dest="theme/synthetic-${theme}.txt"