debian: Fixed lintian priority warning.

priority-extra-is-replaced-by-priority-optional

debian/nginx-module.control.in

diff --git a/debian/nginx-module.control.in b/debian/nginx-module.control.in
index 469adc5..8c4f074 100644
--- a/debian/nginx-module.control.in
+++ b/debian/nginx-module.control.in
@@ -24,7 +24,7 @@
 Package: nginx-module-%%MODULE%%-dbg
 Architecture: any
 Section: debug
-Priority: extra
+Priority: optional
 Depends: nginx (= %%BASE_VERSION%%-%%BASE_RELEASE%%~%%CODENAME%%),
          nginx-module-%%MODULE%% (= %%VERSION_PREFIX%%%%MODULE_VERSION%%-%%MODULE_RELEASE%%~%%CODENAME%%),
          ${misc:Depends}

debian/nginx-plus-module.control.in

diff --git a/debian/nginx-plus-module.control.in b/debian/nginx-plus-module.control.in
index cae9cbd..0b24e82 100644
--- a/debian/nginx-plus-module.control.in
+++ b/debian/nginx-plus-module.control.in
@@ -24,7 +24,7 @@
 Package: nginx-plus-module-%%MODULE%%-dbg
 Architecture: any
 Section: debug
-Priority: extra
+Priority: optional
 Depends: nginx-plus-r%%PLUS_VERSION%%,
          nginx-plus-module-%%MODULE%% (= %%VERSION_PREFIX%%%%MODULE_VERSION%%-%%MODULE_RELEASE%%~%%CODENAME%%),
          ${misc:Depends}

debian/nginx.control.in

diff --git a/debian/nginx.control.in b/debian/nginx.control.in
index 68dd9e6..d77e688 100644
--- a/debian/nginx.control.in
+++ b/debian/nginx.control.in
@@ -25,7 +25,7 @@
 Package: nginx-dbg
 Architecture: any
 Section: debug
-Priority: extra
+Priority: optional
 Depends: ${misc:Depends}, nginx (= ${binary:Version})
 Description: nginx debug symbols
  This package contains the debugging symbols for nginx.