Use `python3` instead of `python`

Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/2135

tools/make-chromium.sh

@@ -23,7 +23,7 @@ cp platform/chromium/*.json $DES/
 cp -R $DES/_locales/nb $DES/_locales/no
 
 echo "*** uBlock0.chromium: Generating meta..."
-python tools/make-chromium-meta.py $DES/
+python3 tools/make-chromium-meta.py $DES/
 
 if [ "$1" = all ]; then
     echo "*** uBlock0.chromium: Creating plain package..."

tools/make-opera.sh

@@ -44,6 +44,6 @@ rm $DES/lib/publicsuffixlist/wasm/*.wasm
 rm $DES/lib/publicsuffixlist/wasm/*.wat
 
 echo "*** uBlock0.opera: Generating meta..."
-python tools/make-opera-meta.py $DES/
+python3 tools/make-opera-meta.py $DES/
 
 echo "*** uBlock0.opera: Package done."

tools/make-thunderbird.sh

@@ -27,7 +27,7 @@ cp -R $DES/_locales/nb             $DES/_locales/no
 rm $DES/img/icon_128.png
 
 echo "*** uBlock0.thunderbird: Generating meta..."
-python tools/make-firefox-meta.py $DES/
+python3 tools/make-firefox-meta.py $DES/
 
 if [ "$1" = all ]; then
     echo "*** uBlock0.thunderbird: Creating package..."