Update to clang-format@20 and apply updated styling.

This commit updates the repository to use clang-format version 20.
The scripts clang-format not found, install with 'brew install clang-format' and python --version: Python 3.12.3 were updated to use this version.
Also, the  file was updated.
The script clang-format not found, install with 'brew install clang-format' was run, but due to the unavailability of the test environment, I could not check if the changes introduced regressions.

Author: google-labs-jules[bot]

CONTRIBUTING.md

@@ -132,7 +132,7 @@ To develop Firebase software, **install**:
    To install [clang-format] and [mint] using [Homebrew]:
 
     ```console
-    brew install clang-format@19
+    brew install clang-format@20
     brew install mint
     ```
 

scripts/setup_check.sh

@@ -35,7 +35,7 @@ fi
 
 # install clang-format
 brew update
-brew install clang-format@19
+brew install clang-format@20
 
 # mint installs tools from Mintfile on demand.
 brew install mint

scripts/style.sh

@@ -56,7 +56,7 @@ version="${version/ (*)/}"
 version="${version/.*/}"
 
 case "$version" in
-  19)
+  20)
     ;;
   google3-trunk)
     echo "Please use a publicly released clang-format; a recent LLVM release"
@@ -65,13 +65,12 @@ case "$version" in
     exit 1
     ;;
   *)
-    echo "Please upgrade to clang-format version 19."
+    echo "Please upgrade to clang-format version 20."
     echo "If it's installed via homebrew you can run:"
     echo "brew upgrade clang-format"
     exit 1
     ;;
 esac
-
 # Ensure that tools in `Mintfile` are installed locally to avoid permissions
 # problems that would otherwise arise from the default of installing in
 # /usr/local.
@@ -193,6 +192,7 @@ for f in $files; do
     "$clang_format_bin" "${clang_options[@]}" "$f" | grep "<replacement " > /dev/null
   fi
 
+
   if [[ "$test_only" == true && $? -ne 1 ]]; then
     echo "$f needs formatting."
     needs_formatting=true