vulkan: always enable GL_EXT_shader_explicit_arithmetic_types

Implicit types were a mistake.
lowp/mediump/highp was a sin.

libavutil/vulkan.c

@@ -1479,6 +1479,7 @@ int ff_vk_shader_init(FFVulkanContext *s, FFVulkanShader *shd, const char *name,
     GLSLC(0, #define IS_WITHIN(v1, v2) ((v1.x < v2.x) && (v1.y < v2.y))       );
     GLSLC(0,                                                                  );
     GLSLC(0, #extension GL_EXT_scalar_block_layout : require                  );
+    GLSLC(0, #extension GL_EXT_shader_explicit_arithmetic_types : require     );
     if ((s->extensions & FF_VK_EXT_DEBUG_UTILS) &&
         (s->extensions & FF_VK_EXT_RELAXED_EXTENDED_INSTR))
         GLSLC(0, #extension GL_EXT_debug_printf : require                     );