Coding Standards: fix <br/> in core files

[man4toman]

In order to ​self-closing-elements, a single space should precede the self-closing slash.

I created this patch for version 5.0.3, but this version isn't on ticket version selector.

[mukesh27]

Patch.

[mukesh27]

@man4toman, I audited all <br/> occurrences in the following files:

• src/wp-admin/custom-background.php
• src/wp-admin/edit-comments.php
• src/wp-admin/includes/class-wp-filesystem-base.php
• src/wp-admin/includes/class-wp-ms-users-list-table.php
• src/wp-admin/includes/class-wp-plugins-list-table.php
• src/wp-admin/install.php
• src/wp-admin/network/settings.php
• src/wp-admin/network/site-info.php
• src/wp-admin/options-reading.php
• src/wp-includes/widgets/class-wp-widget-archives.php

[mukesh27]

#46105 was marked as a duplicate.

[SirLouen]

Duplicate of #56457.

Basically, I've found that in this was already sorted here [54062]

[sabernhardt]

add space in <br/> for wp-admin/network/settings.php

[sabernhardt]

[54062] missed one <br/> that these patches fixed, in the network settings page, so I updated the patch.

(For an alternative approach, the label and checkbox probably could be wrapped in a div instead of using line breaks.)

[sabernhardt]

removes slashes from <br> in Twenty Nineteen single.php template

[sabernhardt]

[54062] missed one <br/> that these patches fixed

I did not mention earlier that Twenty Nineteen also has two <br/> breaks in its single.php template. However, the theme uses <br> for the other four line breaks.

I added a patch for that too, on this ticket, but it could have its own separate commit.