[fix] templates: remove unneeded escape \' of single quotation mark

Strings like::

    'Query in the page\'s title'

are hard to read / remove escape sequence by using double quotation marks for
strings ::

    "Query in the page's title"

BTW: remove a leading dot in the simple theme [1].

[1] https://github.com/searxng/searxng/pull/485/files/80fb77476fad4b229418c530f3ffda67f357a15a#r756112716



Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>