feedback-box.html: Use plain text translations for text inserted into…

… the email body

_includes/feedback-box.html

@@ -3,11 +3,11 @@
 {% assign reppattern = "$1|" | append: feedbackmail%}
 {%- capture helpdesc -%}{% include_cached t.html t="Please share your ideas, suggestions, or comments via e-mail to the publicly-archived list [$1](mailto:$1$2) or via GitHub." replace=reppattern lang=page.lang %}{%- endcapture -%}
 {%- capture mailbody -%}
-{% include_cached t.html t="[include a relevant email Subject]" lang=page.lang hideTranslationHints=true %}
+{% include_cached t.html t="[include a relevant email Subject]" lang=page.lang plainText=true hideTranslationHints=true %}
 
-{% include_cached t.html t="[put comment here...]" lang=page.lang hideTranslationHints=true %}
+{% include_cached t.html t="[put comment here...]" lang=page.lang plainText=true hideTranslationHints=true %}
 
-{% if feedbackmail == "[email protected]" %}{% include_cached t.html t="I give permission to share this to a publicly-archived e-mail list." lang=page.lang hideTranslationHints=true %}{% endif %}
+{% if feedbackmail == "[email protected]" %}{% include_cached t.html t="I give permission to share this to a publicly-archived e-mail list." lang=page.lang plainText=true hideTranslationHints=true %}{% endif %}
 {%- endcapture -%}
 {%- assign mailbody = mailbody | url_encode | replace: "+", "%20" -%}
 {%- assign mailparams = "?body=" | append: mailbody -%}