Replace "Checkout" by "Check out" when used as a verb

One occurrence in core JGit, several in jgit.pgm. One unused
occurrence in jgit.pgm; remove it.

Change-Id: I04c3dd9d9f542f1e1ac6df4cbf03bcefb6bfdf78
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

org.eclipse.jgit.pgm/resources/org/eclipse/jgit/pgm/internal/CLIText.properties

@@ -24,7 +24,6 @@ branchNameRequired=branch name required
 branchNotFound=branch ''{0}'' not found.
 cacheTreePathInfo="{0}": {1} entries, {2} children
 cannotBeRenamed={0} cannot be renamed
-cannotChekoutNoHeadsAdvertisedByRemote=cannot checkout; no HEAD advertised by remote
 cannotCombineSquashWithNoff=You cannot combine --squash with --no-ff.
 cannotCreateCommand=Cannot create command {0}
 cannotCreateOutputStream=cannot create output stream

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/internal/CLIText.java

@@ -138,7 +138,6 @@ public class CLIText extends TranslationBundle {
 	/***/ public String cacheTreePathInfo;
 	/***/ public String configFileNotFound;
 	/***/ public String cannotBeRenamed;
-	/***/ public String cannotChekoutNoHeadsAdvertisedByRemote;
 	/***/ public String cannotCombineSquashWithNoff;
 	/***/ public String cannotCreateCommand;
 	/***/ public String cannotCreateOutputStream;