Fix typos in the documentation: though -> through

Closes gh-1510

spring-boot-docs/src/main/asciidoc/build-tool-plugins.adoc

@@ -265,7 +265,7 @@ to override version numbers if necessary.
 === Default exclude rules
 Gradle handles ``exclude rules'' in a slightly different way to Maven which can cause
 unexpected results when using the starter POMs. Specifically, exclusions declared on
-a dependency will not be applied when the dependency can be reached though a different
+a dependency will not be applied when the dependency can be reached through a different
 path. For example, if a starter POM declares the following:
 
 [source,xml,indent=0,subs="verbatim,attributes"]

spring-boot-docs/src/main/asciidoc/getting-started.adoc

@@ -549,7 +549,7 @@ file named `src/main/java/Example.java`:
 	}
 ----
 
-Although there isn't much code here, quite a lot is going on. Let's step though the
+Although there isn't much code here, quite a lot is going on. Let's step through the
 important parts.
 
 

spring-boot-docs/src/main/asciidoc/howto.adoc

@@ -1504,7 +1504,7 @@ would only ever be a development time trick probably).
 
 [[howto-reload-springloaded-gradle-and-intellij]]
 ==== Configuring Spring Loaded for use with Gradle and IntelliJ
-You need to jump though a few hoops if you want to use Spring Loaded in combination with
+You need to jump through a few hoops if you want to use Spring Loaded in combination with
 Gradle and IntelliJ. By default, IntelliJ will compile classes into a different location
 than Gradle, causing Spring Loaded monitoring to fail.