[Build] Remove the additional space character in the mirrors.list file (sonic-net#13812)

Why I did it
Fix all mirror is commented out in sources.list in slave image issue. It will have an issue when installing more packages in the slave container.

It will add additional space character after running add-apt-repository command.

For example:
The original config in /etc/apt/sources.list

#deb [arch=amd64] http://deb.debian.org/debian/ bullseye main contrib non-free
Run the following command:

add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian bullseye stable"
Then the setting changed to: (added a new space character after #)

# deb [arch=amd64] http://deb.debian.org/debian/ bullseye main contrib non-free
How I did it
Fix the regex string to add the space pattern. After fixed, whether there is a space character or not, it will not be an issue.

How to verify it

Author: xumia

src/sonic-build-hooks/scripts/buildinfo_base.sh

@@ -71,15 +71,15 @@ check_if_url_exist()
 set_reproducible_mirrors()
 {
     # Remove the charater # in front of the line if matched
-    local expression="s/^#\(.*$REPR_MIRROR_URL_PATTERN\)/\1/"
+    local expression="s/^#\s*\(.*$REPR_MIRROR_URL_PATTERN\)/\1/"
     # Add the character # in front of the line, if not match the URL pattern condition
     local expression2="/^#*deb.*$REPR_MIRROR_URL_PATTERN/! s/^#*deb/#&/"
     local expression3="\$a#SET_REPR_MIRRORS"
     if [ "$1" = "-d" ]; then
         # Add the charater # in front of the line if match
         expression="s/^deb.*$REPR_MIRROR_URL_PATTERN/#\0/"
         # Remove the character # in front of the line, if not match the URL pattern condition
-        expression2="/^#*deb.*$REPR_MIRROR_URL_PATTERN/! s/^#(#*deb)/\1/"
+        expression2="/^#*deb.*$REPR_MIRROR_URL_PATTERN/! s/^#\s*(#*deb)/\1/"
         expression3="/#SET_REPR_MIRRORS/d"
     fi