Remove superfluous backtick in README.md (#1205)

Author: nedtwigg

plugin-gradle/README.md

@@ -135,7 +135,7 @@ All the generic steps live in [`FormatExtension`](https://javadoc.io/doc/com.dif
 
 Spotless requires JRE 8+, and Gradle 6.1.1+.  Some steps require JRE 11+, `Unsupported major.minor version` means you're using a step that needs a newer JRE.
 
-If you're stuck on an older version of Gradle, `id 'com.diffplug.gradle.spotless' version '4.5.1'` supports all the way back to Gradle 2.x`.
+If you're stuck on an older version of Gradle, `id 'com.diffplug.gradle.spotless' version '4.5.1'` supports all the way back to Gradle 2.x.
 
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