mesa: remove the noClamp parameter to _mesa_pack_rgba_span_float()

It was only set to GL_TRUE in one place where it isn't really needed
(glGetTexImage(sRGB format)).
diff --git a/src/mesa/main/histogram.c b/src/mesa/main/histogram.c
index febf8d9..905c1ad 100644
--- a/src/mesa/main/histogram.c
+++ b/src/mesa/main/histogram.c
@@ -684,7 +684,7 @@
       minmax[1][BCOMP] = CLAMP(ctx->MinMax.Max[BCOMP], 0.0F, 1.0F);
       minmax[1][ACOMP] = CLAMP(ctx->MinMax.Max[ACOMP], 0.0F, 1.0F);
       _mesa_pack_rgba_span_float(ctx, 2, minmax,
-                                 format, type, values, &ctx->Pack, 0x0, GL_FALSE);
+                                 format, type, values, &ctx->Pack, 0x0);
    }
 
    if (ctx->Pack.BufferObj->Name) {