OsmoGsmTester: install.adoc: Remove trailing whitespace

My editor is removing it automatically.

Change-Id: I25c8d179a21c66ab3424204e12215f8e1ddd8e54
diff --git a/doc/manuals/chapters/install.adoc b/doc/manuals/chapters/install.adoc
index ae8412a..b2f0082 100644
--- a/doc/manuals/chapters/install.adoc
+++ b/doc/manuals/chapters/install.adoc
@@ -605,4 +605,3 @@
 === osmo-bts-trx
 
 TODO: describe B200 family
-