avfilter/scale_eval: remove redundant mathematical constants

Even though removed from vf_scale in 3b316f9f, they were reintroduced
when scale.c, now scale_eval.c, was split off in 037bb402

libavfilter/scale_eval.c

@@ -25,9 +25,6 @@
 #include "libavutil/pixdesc.h"
 
 static const char *const var_names[] = {
-    "PI",
-    "PHI",
-    "E",
     "in_w",   "iw",
     "in_h",   "ih",
     "out_w",  "ow",
@@ -43,9 +40,6 @@ static const char *const var_names[] = {
 };
 
 enum var_name {
-    VAR_PI,
-    VAR_PHI,
-    VAR_E,
     VAR_IN_W,   VAR_IW,
     VAR_IN_H,   VAR_IH,
     VAR_OUT_W,  VAR_OW,
@@ -68,9 +62,6 @@ enum var_name {
  * non-scale2ref specific values.
  */
 static const char *const var_names_scale2ref[] = {
-    "PI",
-    "PHI",
-    "E",
     "in_w",   "iw",
     "in_h",   "ih",
     "out_w",  "ow",
@@ -124,9 +115,6 @@ int ff_scale_eval_dimensions(void *log_ctx,
         main_desc = av_pix_fmt_desc_get(main_link->format);
     }
 
-    var_values[VAR_PI]    = M_PI;
-    var_values[VAR_PHI]   = M_PHI;
-    var_values[VAR_E]     = M_E;
     var_values[VAR_IN_W]  = var_values[VAR_IW] = inlink->w;
     var_values[VAR_IN_H]  = var_values[VAR_IH] = inlink->h;
     var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;