Fix recenty added .notice admin notice position on theme pages

[sippis]

New admin notices with class .notice overlaps with header on themes page.

In wp-admin/css/common.css after line 42, there should be line .themes-php div.notice, right now the style rules are targeting only to old notices (.error and .updated).

/* Position admin messages */
.themes-php div.updated,
.themes-php div.error {
	margin: 0 0 20px 0;
	clear: both;
}

Relevant ticket from the past; #26304

[SergeyBiryukov]

Related: [30505].

[SergeyBiryukov]

In 31054:

Themes: Fix position of admin notice with .notice class.

fixes #30895.

[SergeyBiryukov]

Moving for 4.1.1 consideration.

[jorbin]

In 31080:

Themes: Fix position of admin notice with .notice class.

merges [31054] to the 4.1 branch

props SergeyBiryukov
fixes #30895.

[dd32]

In 31435:

Revert [31080] from the 4.1 branch and replace it with a small function in an already changed file.
By doing this, we avoid shipping 400KB of changed CSS for such a minor css addition.

See ​https://build.trac.wordpress.org/changeset/31061 for the full size of [31080] in build.
See #30895.