only-en KNW-2014 fix alt text quotation marks

Author: eseyffarth

src/common/en/product_usage_analytics.asciidoc

@@ -58,7 +58,7 @@ The decision to transmit usage data is up to those users of your site who have a
 As soon as an administrator logs into the web interface of your {CMK} site after the first 30 days, a pop-up about product usage analytics appears.
 
 .Pop-up for transmitting product usage data to {comfull}
-image::product_usage_analytics_popup.png[alt=“The pop-up for analyzing product usage data appears when logging in after 30 days.”,fullscreen=1]
+image::product_usage_analytics_popup.png[alt="The pop-up for analyzing product usage data appears when logging in after 30 days.",fullscreen=1]
 
 If you select the option [.guihint]#Remind me again in 30 days#, your site will continue to not collect or transmit any usage data.
 After another 30 days, the modal dialog will appear again.
@@ -69,7 +69,7 @@ There are three options available here.
 The option [.guihint]#Disabled. Reminder scheduled# is preselected.
 
 .Settings for transmitting product usage data
-image::product_usage_analytics_settings.png[alt=“In the global settings of your site, you will find the page for configuring the transmission of product usage data”]
+image::product_usage_analytics_settings.png[alt="In the global settings of your site, you will find the page for configuring the transmission of product usage data"]
 
 To enable the transmission of usage data, select the option [.guihint]#Allow collection and transmission of product usage data#.
 You can then enter details about the [.guihint]#HTTP proxy# to be used.