Update Photo strings in help documents
Due to the real value is the "Image", we need to update several "Photo" strings in help documents.
#. (itstool) path: item/p
#: C/scanning.page:18
msgid ""
"Click the arrow to the right of the \"Scan\" button and choose the type of "
"document you are scanning: <em>Photo</em> or <em>Text</em>."
#. (itstool) path: page/p
#: C/scanning.page:29
msgid ""
"The document type can be also be changed from the <guiseq><gui>Document</"
"gui> <gui>Scan</gui></guiseq> menu. Choose <gui><em>Text</em></gui> if you "
"want the document to be quickly scanned in black and white; choose "
"<gui><em>Photo</em></gui> for a high resolution color scan. See <link xref="
"\"dpi\"/> for more details and more options."
#. (itstool) path: page/p
#: C/dpi.page:11
msgid ""
"The default resolution for document type <gui><em>Text</em></gui> is 150 dpi "
"(dots per inch) and for document type <gui><em>Photo</em></gui> is 300 dpi. "
"You can change these settings from the <guiseq><gui>Document</"
"gui><gui>Preferences</gui><gui>Quality</gui></guiseq> menu."
#. (itstool) path: page/p
#: C/dpi.page:18
msgid ""
"The available scanning resolutions for both document types (Text and Photo) "
"are the same and are listed in the following table:"
#. (itstool) path: note/p
#: C/dpi.page:52
msgid ""
"<gui><em>Text</em></gui> documents are always scanned in black and white, "
"while <gui><em>Photo</em></gui> documents are always scanned in color, at "
"any resolution!"