Auto merge of #13834 - upsuper:unprefix-text-align-last, r=emilio

Unprefix text-align-last for geckolib

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[`text-align-last` has been unprefixed](https://bugzilla.mozilla.org/show_bug.cgi?id=1039541) since Firefox 49.

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- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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components/style/properties/longhand/inherited_text.mako.rs

@@ -395,11 +395,10 @@ ${helpers.single_keyword("text-justify",
                          products="servo",
                          animatable=False)}
 
-${helpers.single_keyword("-moz-text-align-last",
+${helpers.single_keyword("text-align-last",
                          "auto start end left right center justify",
                          products="gecko",
                          gecko_constant_prefix="NS_STYLE_TEXT_ALIGN",
-                         gecko_ffi_name="mTextAlignLast",
                          animatable=False)}
 
 <%helpers:longhand name="-servo-text-decorations-in-effect"