rustdoc: Fix invalid HTML in stability notices

`em` tags cannot contain `p` tags so just use a `div` instead.

src/librustdoc/html/render.rs

@@ -1655,8 +1655,13 @@ fn document_full(w: &mut fmt::Formatter, item: &clean::Item) -> fmt::Result {
 }
 
 fn document_stability(w: &mut fmt::Formatter, cx: &Context, item: &clean::Item) -> fmt::Result {
-    for stability in short_stability(item, cx, true) {
-        write!(w, "<div class='stability'>{}</div>", stability)?;
+    let stabilities = short_stability(item, cx, true);
+    if !stabilities.is_empty() {
+        write!(w, "<div class='stability'>")?;
+        for stability in stabilities {
+            write!(w, "{}", stability)?;
+        }
+        write!(w, "</div>")?;
     }
     Ok(())
 }
@@ -1855,7 +1860,7 @@ fn short_stability(item: &clean::Item, cx: &Context, show_reason: bool) -> Vec<S
                 String::new()
             };
             let text = format!("Deprecated{}{}", since, Markdown(&deprecated_reason));
-            stability.push(format!("<em class='stab deprecated'>{}</em>", text))
+            stability.push(format!("<div class='stab deprecated'>{}</div>", text))
         };
 
         if stab.level == stability::Unstable {
@@ -1880,7 +1885,7 @@ fn short_stability(item: &clean::Item, cx: &Context, show_reason: bool) -> Vec<S
                 String::new()
             };
             let text = format!("Unstable{}{}", unstable_extra, Markdown(&unstable_reason));
-            stability.push(format!("<em class='stab unstable'>{}</em>", text))
+            stability.push(format!("<div class='stab unstable'>{}</div>", text))
         };
     } else if let Some(depr) = item.deprecation.as_ref() {
         let note = if show_reason && !depr.note.is_empty() {
@@ -1895,7 +1900,7 @@ fn short_stability(item: &clean::Item, cx: &Context, show_reason: bool) -> Vec<S
         };
 
         let text = format!("Deprecated{}{}", since, Markdown(&note));
-        stability.push(format!("<em class='stab deprecated'>{}</em>", text))
+        stability.push(format!("<div class='stab deprecated'>{}</div>", text))
     }
 
     stability

src/librustdoc/html/static/rustdoc.css

@@ -523,20 +523,20 @@ body.blur > :not(#help) {
 	padding: 20px;
 }
 
-em.stab {
-	display: inline-block;
+.stab {
+	display: table;
 	border-width: 1px;
 	border-style: solid;
 	padding: 3px;
 	margin-bottom: 5px;
 	font-size: 90%;
-	font-style: normal;
 }
-em.stab p {
+.stab p {
 	display: inline;
 }
 
 .module-item .stab {
+	display: inline;
 	border-width: 0;
 	padding: 0;
 	margin: 0;

src/librustdoc/html/static/styles/main.css

@@ -30,10 +30,6 @@ h2, h3:not(.impl):not(.method):not(.type):not(.tymethod), h4:not(.method):not(.t
     background-color: white;
 }
 
-div.stability > em > code {
-    background-color: initial;
-}
-
 .docblock code, .docblock-short code {
     background-color: #F5F5F5;
 }
@@ -129,5 +125,5 @@ a.test-arrow {
     background-color: white;
 }
 
-em.stab.unstable { background: #FFF5D6; border-color: #FFC600; }
-em.stab.deprecated { background: #F3DFFF; border-color: #7F0087; }
+.stab.unstable { background: #FFF5D6; border-color: #FFC600; }
+.stab.deprecated { background: #F3DFFF; border-color: #7F0087; }