Fix wrong file mode

Normal source files shouldn't have executable bit.

Change-Id: If1d86bd52a47fc11fbde7823f8f4d7ffd94ed394
diff --git a/src/main/java/com/googlesource/gerrit/plugins/importer/HttpResponse.java b/src/main/java/com/googlesource/gerrit/plugins/importer/HttpResponse.java
old mode 100755
new mode 100644
diff --git a/src/main/java/com/googlesource/gerrit/plugins/importer/HttpSession.java b/src/main/java/com/googlesource/gerrit/plugins/importer/HttpSession.java
old mode 100755
new mode 100644
diff --git a/src/main/java/com/googlesource/gerrit/plugins/importer/RemoteApi.java b/src/main/java/com/googlesource/gerrit/plugins/importer/RemoteApi.java
old mode 100755
new mode 100644
diff --git a/src/main/java/com/googlesource/gerrit/plugins/importer/RestResponse.java b/src/main/java/com/googlesource/gerrit/plugins/importer/RestResponse.java
old mode 100755
new mode 100644
diff --git a/src/main/java/com/googlesource/gerrit/plugins/importer/RestSession.java b/src/main/java/com/googlesource/gerrit/plugins/importer/RestSession.java
old mode 100755
new mode 100644